^^^w^^^\^ ^ 9 1 -V V-' ^ x-^^' '^^. 0^^, '^ ^ ^-S " ^ T "^ iV^^\^^^ "^'^ \%s ■x^^ -?:i,7^ /\ -X' ■^^ ^^/^«?'%^^' >^^^\* .^ ^%f/h "o "^. ■-<^^. ';^^^^^^^^ B i> ^^ .^^^^ ,>^ ^ ^^/r^. .^ .^^^.^■^ %'^^^:^' ■ft '<V> ^^ # ^"# l)b.Plato. c c.Arclmiiedes . iee.Acistarchiu if f-CopemiCTis oi D ."Kepler ppjrlai^e jNixbiiLtn-.w^rltoirolycus . q;(];.Ticho . rr.^Mare SerenilatLS -axL.PetaTTns . s s . Posid.C7ni\i s . d cLife.re Tmbriii n.. o o.^laxe Hum qtuul y y. TheopMhLs . s s". Atlas . THE COMMON SIGHTS IN THE HEAVENS, AND HOAV TO SEE AND KXOW THEM, CAPTAIN A. W.^^DRAYSOX, E.A, }^^^ LONDON: CHAPMAN AND HALL, 193 PICCADILLY. 1862. LOKDON : PRINTED BT WILLIAM CLOWES AND SONS, STAMFORD STRKET. PEEFACE. In the following pages will he found a simple description of the various sights which can be viewed in the heavens during the day and night. When possible the pencil has been used to aid the description given by the pen. This book merely pretends to give an ac- count of those objects which may be seen with a common telescope^ or even by the unaided eye. All scientific terms have been as much avoided as possible ; and although in some instances diagrams which look suspicious^ and appear to tend towards geometry, have been inserted, still a moment's examination will, we trust, prove their innocence, and show that IV PEEFACEo they are quite intelligible even to the most unmathematical mincL Under these circumstances it is hoped that all readers may be able to understand and to feel an interest in those subjects which are here lightly touched upon. COMMON SiaHTS IN THE HEAVENS. CHAPTEE I. Every person who possesses sight is provided with the means of perceiving a whole host of interesting and beautiful celestial objects. If the same individual is disposed to spare a few minutes during the many clear nights in the year, to the examination of the various hea- venly bodies, he will shortly become possessed of such an amount of information that a new sphere of investigation will be introduced to him. If, in addition to these natural gifts, he is fortunate enough to be provided with a comm^on telescope, or possesses about three pounds of s]3are cash, so as to provide himself ^ COMMON SIGHTS with one, he is then armed with sufficient means to enable him to examine closely the chief characteristics of those vast floating bodies which, night after night, apparently move around this world, and reveal their wonders to the gaze of the inquirer. It is a common, but at the same time a very mistaken idea, that all which appertains to the celestial bodies, their movements, condition, and positions at various times, is of such a com- plicated and puzzling nature, that very few minds are capable of comprehending even the elements of the science which treats of this subject. Hence very few individuals are dis- posed, or can afford, to devote several year^ of exhausting study to acquire a knowledge of mathematics, geometry, G-reek, and the many other sciences which they believe are requisite to be known, before they can comprehend even the common interesting portion of that vast page, which extends from the horizon to the point above us in the heavens. To comprehend the science of astronomy (as it IN THE HEAVENS. d is taught) requires of course a considerable pre- paration ; but to be able to enjoy the fruit of this science requires little more than eyes, a telescopCj and a few minutes' attention. There are several other subjects ^Yhich may be said to really occupy nearly the same posi- tion as that assumed for astronomy. Walking, for instance, is a very healthy and useful occu- pation. If, ho^Yever, no person was allowed to walk, or believed that he could not do so until he knew exactly what muscles, nerves, and joints he called into action, — could explain how the will, by a mysterious agency, acted upon the matter composing the body and legs, how much air was displaced by the motion of the body, &c., — we might all become very scientific people ; but probably should soon become im- becile, although we might possibly look with contempt upon the healthy countryman who walked ably, but who knew not the science of that which he was doing. Thus to be able to understand the peculiar beauties of the most interesting objects in the 4 COMMON SIGHTS heavens, is within the grasp of certainly ninety- nine out of every hundred individuals, althougli they may be entirely unacquainted with science, but possess merely common observation. There are in the heavens a variety of beauti- ful objects. During the day there is the glow- ing sun, w^hose heat and light are essential to the production and continuation of animal and vegetable life, whose rays gladden and enliven the earth, and whose daily advent calls forth an harmonious song of praise from a myriad feathered songsters. With a calm, subdued light the crescent- shaped moon may also be seen in the day-time, perhaps half her illuminated surface being then turned towards the earth. When the mighty orb of day has run his course, and has retired from that part of the heavens which appears arched above us, then thousands of less gorgeous objects timidly peep forth from their concealment, and, perceiving the earth in shadow, they hasten to display their pale, brilliant fires, until at last the IN THE HEAVENS. O heaveiis appear studded with thousands upon thousands of sparklmg lights, which, although smaller, are scarcely less bright than the mid- day sun. The evening and the night are the periods when the heavens yield most abundantly a field for amusement, and it is then that the wonders revealed therein can be most calmly contemplated. The lover of natm-e, whose thoughts are given to the examination of terres- trial wonders only, is not able to roam during the darkness of night, and perceive those beauties for which he may be in search ; neither can he, during the somewhat long periods of darkness in winter, find many of those interesting natural objects which abound in summer. Yet it is in these very seasons and times that the heavens offer us so fruitful a source of amusement, and reveal to our gaze so many subjects upon which we may employ our thoughts and researches. Our interest in the celestial bodies is much increased when we know that many of these are worlds like that on which we live, and that (J COMMON SIGHTS they differ apparently from it merely in some minor details, or in the presence or absence of certain conditions, which will be, or may have been, those of tliis globe in the coming ages of the future, or in the no less vast and mysterious epochs of the past. To the most su23erficial observer, there appear to be merely three descriptions of bodies in the heavens, viz., the sun, the moon, and the stars. The latter appear to vary from each other in size and brightness as well as in colour ; but unless some slight attention be directed to them, they seem to present very little variety. Observation, however, has shown that the so- called stars must be divided into two classes : the first comprises those bodies which always maintain the same position with regard to each other, and which are at an immense distance from our world, and wliich shine by means of some property inherent in themselves. The second class consists of those so-called stars which move amongst the other stars, and which, it is found, are at certain calculable dis- IX THE HEAVENS. 7 tances from our earth, and which only shine or appear bright because the sun shines upon them. Those of the first class are called ''fixed stars,'' those of the second " -planets ^ * It is found that all the planets move around the sun ; that they all spin round, or rotate, as it is termed, and that thev are all somewhat of the shape of an orange. Many of the planets are attended by certain bodies termed satellites, which move around them just as the planets move round the sun ; these attendants are called " satellites,'' " moons," or " secondaries ;" our moon being a satellite or secondary to the earth. The sun, the planets which move round him, and their satellites or moons, are termed the solar system, which is thus like one family ; the sun the apparent father, or head, the various planets the children, whilst the satellites are the grandchildren. The sun and full moon appear to us nearly of the same size, whilst the various planets * Fi'om 2^^cinetes, wanderers. 8 COMMON SIGHTS differ considerably in their visible dimensions. Appearances are proverbially deceitful, and the proverb holds good most effectually when ap- plied to the celestial bodies. The proportional difference between the size of the sun and the moon, is about that which exists between the ' Great Eastern ' steam-ship and a little boy's toy -boat ; the simiUtude in their apparent size being due to the difference in distance from the earth between the two. We can easily com- prehend the effect of distance in altering the apparent size of objects if we look through our window, where the pane of glass close to us looks larger than a church at a distance. The various planets differ in their size, al- though not so much as the moon and the sun. Still there are some which would cause our earth to look a very insignificant object if the two were placed side by side, and examined from a distance. The accompanying table will show the rela- tive diameter of the sun and the eight primary planets, of wiiich the solar system consists. IN THE HEAYEXS. Miles. Sun about 888,646 Jupiter . ;, 89,000 Satui^n . if 76,000 Xeptune J? 37,500 Uranus . ?-■» 35,000 Eartli . ?? 7,912 Venus . 7,800 Mars ?5 4,189 Mercury ?J 3,140 There are, besides, a number of small planets which revolve round the sun, and are really primaries: these, however, are not considered to rank amongst the eight leading planets in the system ; they are very small, and present peculiarities ^vhich distinguish them from the principal members, and they are, besides, scarcely visible unless with the aid of a tele- scope. Five of the principal planets, viz., Mercury, Yenus, Mars, Jupiter, and Saturn, can be plainly seen with the unaided eye, Uranus is also visible, as a rather dim object ; but, with the aid of a large telescope, reveals a circular and planetary form. 10 COMMON SIGHTS These planets all move round the sun, and at different distances ; the relative position of each is shown below. A different scale is now used to show the distant planets, Jupiter's distance being giA'en. THE SU]S^ Solax Spots . PL2. ■fe-eni ^ooki indi. Changes in a Solar Spot passing across Suns disc. IN THE HEAVENS. 11 CHAPTEK II. THE SUN. Every person must have observed that the sun is higher in the heavens at midday in summer than in winter, and that it remains longer above the horizon in summer than in winter. If the sun be observed during twelve months, it will be found that about the 22nd of December, at midday, it will be lower down than at any other time in the year ; and about June the 21st it will be higher up than at any other time. If we could make two marks in the sky to show the two places where the sun reached at midday, on the 21st of June and 21st of De- ceinber, we should find that about the 20th of March and the 22nd of September the sun was just midway between these marks. If we measured TOth an instrument the dailv 12 COMMON SIGHTS height of the sun, which is always greatest at midday, we should find that, early in January, the sun increased its height yeiy slowly from day to day, and that during a week it yaried a very little more than its own diameter. Then it would go on increasing more quickly until March the 20th, when, durir^g one day, there would be an increase in height equal to nearly the sun's diameter. After this date there would be a gradual de- crease in the rate until June, although still a daily increase in height. AATien, then, we haye passed the shortest day, we do not observe any very great difference in the length of sunlight during a few days ; then there is a slow and steady increase, the dif- ference being greatest during the month of March, when the days increase rapidly in lengi:h ; after this date there is still a gradual increase, but the rate is not so 2:reat. In fact, durinsf the thirty days in March, as great a change occurs in the sun's midday height as there is during the ten days of December, the thirty- IN THE HEAVENS. 13 one days of January, and the eleven days of February. So that in thirty days of March there is as great a change as during the fifty- two days from the 21st of December on to the 11th of February. After the 21st of June the daily greatest height of the sun begins to decrease, and in a manner exactly similar to that in which it in- creased, viz., slowly at first, and quickest when about midw^ay in its course of descent. Thus, in September, there is a very rapid decrease, just as in March there was an increase in the daily height of the sun ; then the rate of de- crease becomes less, until the 21st of Decem- ber. These changes occur year after year with regularity, no difference being observed unless the most accurate instruments are employed. The cause of the sun's variation in height is the movement of the earth round the sun, and in a sort of up-and-down manner. Thus, if w^e call the northern half of the world the upper half, and the southern half the loiver^ then we 14 COMMON SIGHTS may say that on the 21st of December ^Ye are above the smi considerably ; from this elate to the 21st of June the earth moves downwards, and round a circle, in the centre of which is the sun. On the 21st of March the earth is level with the sun. From the 21st June to the 21st December the earth moves upwards, and is again level with the sun on the 21st of September. By means of a common hoop, we may see why the sun rises and falls each day, more quickly, in March and September, than at other times of the vear. ^ 3-^,.^ 4.'--^,. 3"; A Thus, suppose D M J S a hoop resting on a IN THE HEAVENS. 15 table J, and propped up at D above the t<tl:'le, and suppose C the centre of this hoop. If we moved anything from 1) to 1. it would not have moved doivnwards very much, because this part of the hoop is nearly level. As this same thing moved from 1 to 2, it would have moved down- wards much more, although the distances from D to 1 and from 1 to 2 were equal From 2 to 3 there would be a more rajfid fall, whilst from 3 to 4 a more gradual descent. At X the body would be level with C, at D above it. and at J below it. This is just the eom\se that the earth pursues round the sim ; D being the December, M the March, J the June, and S the September posi- tion ; C being the position oi the sim. The earth is distant from the smi about ninety-five million miles, a distance which would occupy an express train about two hundred years to travel. In consequence of the earth movinj^- round the sim, our annual journey amounts to nearly six hundred millie^n miks : thus each day of our lives we travel more than a million and 16 COMMON SIGHTS a half miles through space, or a distance equal to about sixty times round the earth. If we stand at some railway crossing and see an express train rush past, the iron horse snort- ing and wdiistling, the dust flying, the wind almost knocking us do^\Ti, and then observe the passengers reclining calmly in the carriages, or talking to each other, we cannot well fail to ponder upon the singular anomaly thus presented to us. There is a mass of carriages which appears to be jolting and crashing onwards to destruc- tion, at the rate of nearly fifty miles an hour, and yet the most timid of the occupants of the carriage appears to suffer no alarm. This is cer- tainly a grand sight, although we are familiarized to it, and therefore are but slightly impressed with the indication of power thus manifested. If, however, an express train dashing past us is at all a source of admiration, how much more impressed we should be, were we able to observe from space, a vast world which would come rushing and spinning past us, with a ve- locity of sixty-eiglit thousand miles an hour ! IX THE HEAYEXS. 17 Every human being, therefore, is a great tra- veller, although he may repose in his arm-chaii' from day to day. The cannon-ball that moves too quickly to be seen is merely a slow coach compared to the world upon which we live, and our world is slow when compared to the little planet 3Iercury, whose rate is nearly double that of the earth. At noon the sun will be south of all localities in England. The sun appears to move round the earth in twenty-four hours; therefore, in six hours it moves round one fourth of the earth, and consequently will be found near the Avest at six o'clock in the evening, and near the east at six o'clock in the morning. If we know the time, therefore, and can see the sim, we can always tell where the cardinal points of the compass are situated ; for as the sun is south at noon, and near the east at 6 a.m.. it would be nearly south-east at 9 A.ir., between south-east and south at half-past 10 A.:yi., and so on. If the time of sunrise be added to that of c 18 COMMON SIGHTS sunset, the sum of the two will nearly always amount to twelve. Thus, if the sun rise at 8 A.M., it will set about 4 p.m. ; and if it rise at 5 A.M., it will set about 7 p.m. : thus, if we know the time of sunrise we may obtain that of sunset, or vice versa, because the sum of the two should amount to twelve. We will first call attention to those interest- ing facts which may be seen by the unaided eye, before v»'e refer to those which require some artificial means to enable a person to see them distinctly. Among the most singular phenomena con- nected with the sun, the midnight sun to an in- habitant from the central portions of the globe must appear at first very curious. In England we are accustomed to have twilight from about the 21st of May until the 21st of July, during which period the nights are nearly as light as many of our November days. This, however, is very different from seeing the sun above the horizon at midnight, and shining as brightly as he does in England towards the afternoon of IN THE HEAVENS. 19 an autumn day. To view the midnight sun we must trayel to within about twenty-three and a half degrees from the north or south poles — that is, we must travel to about sixty-six and a half degrees of north or south latitude. In Spitz- bergen, the north of Iceland, the north of Norway, in Baffin's Bay and Greenland, the midnight sun will be visible during June. The farther north that we go from England, the lighter will be the nights during the sum- mer. When w^e are at the central — i. e,, the equa- torial — latitudes of the earth, we have the sun directly overhead dming midday in March and September, and a very little way from the same point during midday in June and De- cember. The nights at the equator are dark as Erebus. If the moon does not shine, and if there be a few clouds to cause the stars to look dim, then an English winter's night is twilight compared to the summer night at the equator. At sunset, also, the sun, instead of passing 20 COMMON SIGHTS obliquely below the horizon, descends perpen- dicularly — so that twilight has scarcely any existence at or near the equator. In England, and in localities in the northern half of the world, it is customary to talk about turning a screw, or dealing at whist, &c., with the sun — that is, from left hand to right. When, however, we have crossed the equator, and have travelled some sixteen hundred miles on the other side, these directions become incorrect, for the sun there appears to rise from the right hand and to set on the left, and to pass at all times of the year from right to left, instead of from left to right. Exactly the same change in right and left movement would occur if a weight were to be swung backwards and forwards between two people who were standing face to face. Each time the weight moved to the right of the one person it would move to the left of the other, and vice versa. This change in the apparent movement of the sun having been observed is a rather con- IN THE HEAVENS. 21 vincing proof that the Phoenicians rounded the Cape of Good Hope as long ago as 400 B.C. — that is, upwards of U\o thousand two hundred and sixty years ago ; for Herodotus states that there were some travellers who sailed down the Eed Sea and returned by Gibraltar, and stated a thing which he could not believe, though others might — viz., that during their journey they observed the sun rise from their right hand and set upon their left. This fact was not likely to be guessed at by sailors had they not seen it, especially in an age when it was thought unscientific and foolish to beheve that the earth was spherical instead of a plane, and when scarcely a single traveller had crossed the equator, or even ventured within the tropics. The sun sometimes, when rising or setting, appears of a blood-red colour, and of a very large size. If measured with an instrument at this period the sun is really not larger than at another time ; it therefore follows that there must be some effect produced upon the eye, 22 COMMON SIGHTS which, is not a real enlargement in the actual size of the sun, or in its measured size. These considerations induced the earlier astronomers to believe that the large size was a delusion caused by the sun being compared with terrestrial objects when he was near the horizon, whilst when he was eleyated in the heavens there were no objects with which to compare him. A veiy little consideration would soon have shown that this could not be the true explana- tion of the phenomenon ; for in consequence of the sun setting every evening, and rising every morning, the same effects ought always to be observed, whereas it is only two or thi^ee times each year that this singular effect is seen. From another fact, also, the inefficiency of this explanation would have been manifest — viz., that the large red sun is observed very frequently at sea, when the ocean is calm as a lake, and no terrestrial or other objects are within a hundi^ed miles. It is far more probable that the enlarged IX THE HEAYEXS. 23 appearance is due to a peculiar state of the atmosphere, a condition probably analogous to that which enables us at times to perceive quite distinctly distant objects, which then appear larger than usual. When this condition exists, the ^'weather-wise" prophecy a change of w^eather, and usually consider that rain will shortly fall. A register of the weather before and after this singular appearance of the suu might enable us to collect some useful facts. When the sun is just close to the horizon he appears usually to be egg-shaped, instead of circular, his longest portion being parallel to the horizon. This effect is due to what is called refraction. Eefraction is the term used to indicate the bending of the rays of light as they pass thi^ough the atmosphere or through water. The nearer any celestial body may be to the horizon the more would a ray of light from it become bent ; and thus, as the lower part of the sun is nearer the horizon than the upper part, then the light from the lower part becomes the more bent, whereas no difference 24 COMMON SIGHTS is produced upon the horizontal width of the sun. The following sketch shows the appear- ance referred to. The sun is there shown just resting on the horizon, and its shape altered from a circle to an oval. Accordino- to the ;# ,- "^^^W^^fe^ state of the atmosphere this apparent distortion increases or diminishes, but it is usually very considerable. The most singular fact connected with it is that when just visible above the horizon, as shown in the sketch, the sun is actually below the horizon, and is brought into view by refraction. A very rare and singular appearance is that called parhelion — near the sun. Sometimes IN THE HEAVENS. 25 two, three, or more suns are visible in the heavens at the same time. In high latitudes this appearance is not uncommon, but in lower regions it is rarely witnessed. Aristotle men- tions an instance of two mock suns having been seen the whole day on the Bosphorus ; and Pliny tells of a triple sun having been seen by him during the reign of Claudius. Hevelius, an astronomer of celebrity at Dantzic, relates that seven mock suns were once noticed by him. These mock suns usually appear on each side of the real sun, or above and below it, and thus rest upon the circumference of a halo which surrounds the sun. When examined by the unaided eye the sun appears a brilliant luminous body, without a speck. If, however, a telescope be directed to him, and if the eye be protected by means of a piece of dark glass, the sun then presents a sort of mottled surface, which is by no means perfectly clear, but which appears at all times to be covered by a series of dark and irregular lines ; and at uncertain periods black spots of 26 COMMON SIGHTS large size appear upon his surface. The smaller streaks visible on the sun do not seem to change in any way, nor do they offer any peculiarities which can serve as guides to their constitution. The large spots, however, are usually undergoing changes, and these present phenomena which are well suited for the foun- dation of speculation. The spots upon the sun serve to make us acquainted with one or two facts of interest. They show us that the sun turns upon its axis just as does the earth and the principal planets in the system. They indicate where the equa- tor of the sun is situated, and they enable us to find the length of time occupied during his rotation. It not unfrequently happens that a person possessing good sight can see with the naked eye some one or two spots upon the sun, pro- vided that a piece of coloured glass be used as a means to subdue his brilliancy. When taking altitudes with Hadley's sextant, and without a telescope, I have usually distinguished a spot IX THE HEATEXS. 27 upon the sun ; the combined effect of the red and green glasses being the most favourable for such an examination, as the sim then appears to be a pale yellow, whilst the spot is black. It has been considered remarkable that some of the ancients should have known of the exist- ence of spots on the sun, before the telescope was invented ; but if any person carefully ex- amine the sun's smface each day by the aid of pieces of yellow and red, or red and green glass, or even look at the sun's reflection in a pail of water, it will appear singular how any observer could have omitted to notice the spots, as they can be easily seen with the naked eye. During a London fog, when the sun is only just visible, I have seen the spots very distinctly. To watch the changes which take place, and to see clearly the peculiarities which appertain to the spots, a telescope with a moderately power- ful magnifying power should be used, and a dark eye-piece fitted on to the eye end of the telescope. To observe any celestial body thoroughly, the telescope should be arranged 28 COMMON SIGHTS upon some kind of stand, and protected from the wind. When even a telescope of average power is thus protected, the changes in the spots on the sun may be observed, and a register kept of the maximum and minimum quantity, from which some valuable facts might be adduced. To a person unacquainted with the simplicity of some astronomical problems, it may appear a very difficult matter to tell which is the sun's pole star, and how his equator is arranged relatively to that of the earth. To approxi- mate very closely to both these data is, how- ever, a very easy matter, which is accomplished as follows : — Suppose that upon a common globe we arrange several black spots, and then stand at a distance and watch these spots when the globe is made to turn round. If we walked around the globe, we could soon tell in which direction its axis pointed, for when we found the spots traced straight lines, we should then know that the axis was at right angles to IN THE HEAVENS. 29 these Knes, and we should consequently know in which direction it pointed. So is it mth the spots on the sun, which are found to trace straight lines during June and Decem- ber, and curved lines at all other times of the year. Thus, if from day to day we were to mark on a circle the position of the spots, we should find that a line joining these various positions would appear, as shown below, at the various periods indicated. December. March. June. September. During June and December the spots trace straight lines, which make an angle of about seven degrees with a horizontal line on the earth at midday. During March and September the spots trace curved lines. Thus from the earth we can look upon the north pole of the sun during September, and upon the south pole of the sun during March. 30 COMMON SIGHTS K any particular spot be observed, it is found to move from the left across to the right of th.e sun. The motion is exactly that which would occur if the spots were fixed to a rotatory ball, and it is therefore only reasonable to conclude that the sun turns upon an axis. If any one spot be watched, it is found to return to the same position in a j)eriod a little over twenty-seyen days. Making the proper allowance for the movement of the earth during that time, it is found that the sun turns round in about twenty-five days and a half. The probable object of this rotation will be considered at a future page. A spot if examined with a large telescope is observed to undergo changes in size and shape, but rarely, if ever, to alter its position. When the spot first appears upon the left side of the Sim, there is usually a dark and a light portion, as though some reflected light were cast upon the side of a hollow cylinder. ^^Tien the spot is seen at the central portions of the sun, then it is all black, but usually with a IN THE HEAYEXS. 31 lighter fringe. When on the right side of the sun, it is lighted in the same manner, only upon the opposite side to that upon which it was lighted when it became visible upon the left side. The sketches on Plate 2 ^vill show the apparent changes which usually take place in a spot as it is carried across the face of the sun. Many speculations have been made as to the nature of the solar spots, but up to the present time very Kttle is kno^Ti about them. It may be many years before we ascertain for certain whether they produce any effect upon our cli- mate, or upon the earth at all ; and it is pro- bable that until we have some other means than mere conjecture for arriving at truths con- nected with remote objects, the spots on the sun will still continue to be mysteries. From observations carried on within the last thirty years, there appears some probability that the spots are in the greatest profusion at intervals of about ten years, wliilst in the inter- mediate periods the least number have been observed. In the vear 1828 there were, ac- 32 COMMOiT SIGHTS cording to the observations of M. Schwabe, 225 groups of spots observed: in 1833, only 33 groups. In tiie year 1837 there were 333 groups seen; whilst six years afterwards, viz., in 1843, there were only 34. Again in 1848 there were 330 groups seen. Thus at intervals of nearly ten years the maximum number of spots have been observed. It is a little singular, and it may be con- sidered rather beyond the range of chance, that the greatest magnetic changes on earth are found to correspond with the periods when the maximum and minimum number of spots are observed on the sun. Thus it is highly pro- bable that there is a connection between these two phenomena which may either be both the effects of some other great natural cause, or, as is more probable, that terrestrial magnetism is connected mth the sun's condition. The most popularly received idea about the sun's spots is, that they are openings in a luminous atmosphere by which he is sur- rounded, and that consequently it is the dark IN THE HEAVENS. 33 body of the sun that is seen, in the shape of a spot. There is a great difficulty about this hypothesis, inasmuch as it requires us to as- sume some curious laws to be acting in connec- tion TOth the sun's atmosphere. On earth it is impossible to produce a permanent hole in water, and it is equally as difficult to form a hole in the atmosphere. Unless, therefore, we assume that the sun's atmosphere is sohd, it is doubtful whether a permanent hole could be produced in it. And thus we have to assume an atmosphere of a particular nature before we can imagine any holes to be made in it. Dming the evenings of March and April, and before smirise in October, there appears sometimes a faint luminous cone of light near the sun, which in appearance is not unlike the tail of a comet. In these latitudes this phe- nomenon, called the zodiacal light, is not so often seen as it is in equatorial regions. It has been remarked, that when the sun is free from spots the zodiacal light is rarely seen, but when the opposite condition prevails, then the D 34 COMMON SIGHTS light is frequently observed. The colour is usually of a rose-pink, and it varies in in- tensity according to the state of the atmo- sphere. It is impossible to avoid feeling grateful to the great Euler of the universe, when we realize the vast enlightenment which has taken place in the human mind since the earliest ages of man. We can scarcely bring before us any example which so completely exempHfies this fact as that connected with the present know- ledge of the movements of the heavenly bodies. In the olden times, centuries before England was anything greater than the residence of bar- barians, the movements of the celestial bodies had occupied the attention of the Eastern sages; but in too many instances the slight knowledge which they did possess, was trea- sured merely because it enabled the possessors to wield an influence over the ignorant and bigoted. An eclipse of the sun, which can now be predicted years in advance, and wdthin a minute IX THE HEAYEXS. 35 of the time of its occurrence, was in the olden time a cause of fear and dread, and was made use of as an excuse for sacrificing victims to superstitious bigotry, or for the purpose of extorting obedience from an alarmed and igno- rant public. Those who have studied the history of even modern progress, and have seen how in a com- paratively enlightened age innovations have been scouted, and great truths rejected and abused for years, or until the facts became too powerful to be denied, can imagine what must have been the fmy and astonishment of those antiquated savants who had long taught astro- nomy and astrology, when it was first an- nounced that a solar eclipse was caused by the intervention of the dark body of the moon. This assertion was so utterly at variance with that which was in the earliest ages called real orthodox science, that it merely excited the anger or ridicule of the hearers. There appears to be tolerably good evidence to show, that the Chaldeans were able to foretell 36 COMMON SIGHTS with some certainty both eclipses of the moon and of the sun ; yet when Anaxagoras the Greek announced that it was the moon which caused a solar eclipse, his assertion brought upon him the censure of his countrymen, and he was banished as an infidel. To most modern minds the explanation of an eclipse appears so simple, that we wonder how any other cause could for a moment have been accepted. Yet when the mind has from child- hood been taught that certain effects are due to such and such causes, it is very difficult to up- root this teaching, though to the unprejudiced it may appear absurd and unnatural. It must have indeed been a hard trial for the advanced men of the early ages, who, having patiently thought and carefully observed, at length wished to explain the cause of eclipses. The hearers were so different from a modern audience, that we can only imagine their state if we have witnessed the unreasonable pro- ceedings of some half-savages, upon whom logic, argument, demonstration, or facts would IN THE HEAVENS. 37 produce no more effect than the same weapons upon a herd of swine. Yet what must have been the inward feeling of those few leading minds who had read aright the page of nature ? Observing in some solitary tower, the astro- nomer must have felt himself almost in an- other world as he found his reasoning true, and his calculations connected with the period of an eclipse verified by facts. Still, as in all cases, a price must be paid for the possession of knowledge ; and this solitary student of the heavens must at times have felt lonely, and must have thirsted for a few kindred and ex- panded minds with which to exchange ideas ; for the more elevated become our thoughts the more do we contract the circle of our boon companions. An eclipse of the sun is a sufficiently rare phenomenon to excite universal attention. To astronomers an eclipse becomes interesting in consequence of its being the means whereby they may correct any errors which exist in tlie calculated positions of the sun and moon ; for 38 COMMON SIGHTS although the principal moyements of these two bodies are now well known, still there are some minor changes which occur, and which from time to time require that corrections should be made. The first object observed in a solar eclipse is that the sun has lost its circular form, and appears to have a chip taken out of his western side. This chip becomes larger and larger, and as it does so the sunlight becomes dim, and the landscape is seen by means of an unnatural pale-yellow light. According as the eclipse is partial or total, and according as the moon passes across the upper or lower portion of the sun, so will the commencement of the ecKpse produce a variety of appearances. When the eclipse is at its maximum the sun may be entirely obscured, or may appear as a ring of light, according as the echpse occurs when the moon is at the least or greatest distance from the earth. It is when the sun is almost entirely obscured that some singular appearances have been ob- IN" THE HEAVENS. 39 served at the extremities of the moon. The first of these consists of a number of pro- tuberances, or prominences, which become visible on various parts of the extremities of the moon. These are sometimes of a lake-red colour, sometimes bright red, and at other times nearly white. The sketch, Plate 3, shows the general appearance of these protuberances. Several theories have been invented to ac- count for the observed facts, but, like the spots, all is as yet mere speculation. Some observers have supposed that the red flames have been seen just where there was a large spot on the sun; but it as often happens that where no spots exist there the flames are visible. From careful observations which have been made since 1842, it is probable that the appearance results from some condition existing on the sun, and is not due to anything on the surface of the moon : thus probably they . are merely material objects, perhaps similar to clouds in our atmosphere. The moon is surrounded during a solar eclipse 40 COMMON SIGHTS with a luminous ring, which gives to it a very beautiful appearance. Dr. Halley, speaking of this, says, in reference to an eclipse in 1715 : " Some seconds before the sun was entirely hidden there appeared a luminous ring around the moon, in breadth equal to a twelfth, or perhaps even a tenth of the moon's diameter. Its tint was a pale white, or we may say a pearly white ; it appeared to me to be slightly tinted with iridescent colours." Speculation is still busy in assigning a cause for this appear- ance as well as the former. During future eclipses, amateurs may consider both these phenomena worthy of observation. We will consider more fully those movements of the earth and moon which cause eclipses when we speak of the moon. Eclipses have happened at various remark- able periods, and consequently amongst an ignorant and superstitious race they have been regarded as objects of fear. During my resi- dence on the south-eastern coast of Africa an eclipse of the sun happened, and which I had P1.3. Partial and Total Eclipses of tlie Sim . TinDsnt BxookiiJi The Ted flaraes during Eclipses. IN THE HEAVENS. 41 announced to some of my Ka£6r companions. They were very incredulous that ''the sun would be ill/' until they saw its light begin to decrease, when they were greatly astonished. Theii* inquiries were original and amusing ; some of the men asking why the sun was not well, others wishing to know whether it was tired, and thought it time to lie down behind the hills. When they received an explanation, and were told that in a few days the moon would l>e seen, and that it was her passing before the sun that caused the eclipse, they mostly com- prehended the cause at once ; and one man added in explanation to his hearers that the line of shadow luas cuiwed like the moon. Thucydides states that there was an ecKpse of the sun during the first Peloponnesian war ; and Plutarch informs us that Pericles had some difficulty in persuading the men who were on board his galley to accompany him, as they feared that the sun becoming dark was an evil omen. The o'reat battle of Arbela was fou2:ht eleven days after an eclipse, and thus the date 42 COMMON SIGHTS of the battle becomes known by a reference to the lunar and solar tables. The following are the lyrincipal eclipses of the sun which will be visible in England during the next forty years : — 1865 October 19th.... 4 p.m. 1867 March 6th 8 a.m. 1870 December 22nd . . 11 a.m. 1874 October 10th. ... 9 a.m. 1887 August 19th 3 a.m. 1900 May 28th 3 p.m. There will be other eclipses visible, but merely very partial ones. IJJ THE HEAVEXS. 43 CHAPTER III. "What song the Syrens sung, and what name Achilles assumed when he hid himself among women, although puzzling questions, are not beyond all conjecture." From the region of facts we pass to that of conjectare, and we will now consider the pro- bable condition of our central orb. It is frequently considered a sign of mental weakness to deal with speculations, whilst to collect facts is a proof of sound sense. To speculate when we have no grounds upon which to build is certainly injudicious; but to com- pare probabilities, and to reflect upon the evidence, or upon the condition of the unknown, is a proceeding not unlikely to lead to the dis- covery of truth. Sometimes we find that individuals have been designated speculators, simply because 44 COMMON SIGHTS they differed from the speculations of those who had preceded them, and who imagined that their theory or speculation must rest upon in- controvertible facts. Thus we usually find that the sound, close reasoners of the early ages w^ere designated by certain men visionaries and speculators, whereas these characteristics in reality belonged to those who believed their positions secure and immutable. The earliest scientific men speculated upon the form of the earth ; they agreed that it was flat, and that it rested upon water. Those who at a later period disagreed with this hy- pothesis, and believed that the sphere was the more true form, were regarded as speculators and visionaries, with whom it was useless to reason. In quite modern times the geologist was looked upon as a visionary, and who, like Galileo, was accused of an attempt to disprove Scripture. Now, however, when men's minds are more enlightened, it is found that these very facts revealed by geology prove more IN THE HEAVENS. 45 than ever that an all-powerful Creator, whose wisdom is unbounded, must have made the earth and all it contains upon a prearranged system. It is almost impossible to name any subject upon wliich there have not been some opinions formed: when, therefore, we speculate upon these subjects, and come to a different con- clusion to that previously arrived at, it is merely one idea opposed to another, and we must then consider the probabilities affecting each. Thus a speculation upon the unknown should not be widely or gratuitously condemned, more especially when certain notions are accepted as true, and which are in themselves merely speculations. The cause of the sun's heat is a subject w^hich must possess considerable interest, but which is one coming within the bounds of speculation only. We have therefore to con- sider the probabilities connected with the cause of this heat ; and as a preliminary step we may reflect upon some of the various methods at 46 COMMON SIGHTS present known, and by means of which heat is produced. First we have the common method — viz., by means of fire. It is here necessary that some description of fuel should be supplied, and we are not aware of any means by which a great fire can be maintained except by the aid of fuel. Secondly. Heat may be produced by means of friction, and according to the conditions under which this friction takes place, so the heat evolved is great or otherwise. Thirdly. Great heat is produced in many substances when a current of electricity is passed through them : thus platinum, silver, and substances in which sulphur is contained, will usually become very hot v*hen they are employed as conductors. Fourthly. During many chemical changes great heat is produced and evolved by certain combinations in various substances. These are all simple methods of producing heat ; how many more ways there may be it is IN THE HEAVENS. 47 impossible to say, although it is probable that there are many more, for it is not likely that we have just now reached the end of discovery connected with heat. We may next consider the various facts con- nected with the heat of the sun ; and amongst others we find that when the sun is nearly vertical we feel more heat than when he is near the horizon ; that if we ascend to the summit of lofty mountains we obtain less heat, although the sun may be directly overhead. Even from these two facts we are taught that the heat of the sun is dependent in a great measure upon the state of the atmosphere through which the rays pass, and upon the angle which these rays make with the earth's surface. There is no evidence which should induce us to think that the sun is a great fire, or that it is in itself any hotter than is our earth. The particles of which the sun is composed may be charged with, or they may be producing great quantities of a subtle force somewhat similar to electricity. This force, or power, may produce 48 COMMON SIGHTS no effect on space, but when it enters an atmo- sphere it may at once produce heat and light. We know that a gun may be fired by means of electricity, although it may be at the distance of twenty or thu^ty miles from the battery. The battery itself is quite cool, and so is the copper wire which conducts the electricity. When, however, this subtle current traverses a piece of platinum wire, the wire instantly becomes red hot, and the gun can be fired. If a person w^ere ignorant of the law that the heat induced in any substance by the transmission of an electric current was dependent on the conducting power of the substance, he might imagine that the battery itself must be at a fearful heat in consequence of the wire twenty miles distant becoming red hot. Hence it is not improbable that our great central orb may be a cool summer residence, but possessed of a power which is not (at least yet) manifested by the various planets in the system. It is not improbable that according to the atmospheric or other condition of a planet, so IX THE HEAYEXS. 49 may it be able to gain great or little heat from a certain quantity of the sun's rays. It is absurd to build any theories upon the supposition that because a planet is at a great distance from the sun, that therefore it must be very cold, and vice versa. We may be sure that the architect of the universe made some ar- rangements to overcome this, to us, apparent difficulty. The planet Jupiter is far brighter and appears even better hghted than does the planet 3Iars : and yet the former is not so near to us as is the latter by about three hundred and forty million miles, and Jupiter is rather more than that number of miles farther from the sun than is Mars. It would be indeed singular if om- little earth were the only orb in the system with a climate suitable to what we know of organic life. When, however, we consider that the heat de- rived from the sun may be dependent upon the condition of a planet's atmosphere, we see no difficulties in our way. E 50 COMMON SIGHTS Another singular fact which is interestmg is that the sun rotates upon its axis. To assert that any great work of nature is not made for some definite purpose is very like an endeayour to libel creation. Surely, then, this rotation must be for a purpose ; what that may be is a subject for conjecture. Upon observing the different members of the solar system w^e find that they all move round the sun and in the same direction, the sun itself rotating in the same way as the planets revolye. Thus the yarious ^^lanets seem to roll round their orbits, and in the same dh^ection that the sun itself rotates. The rotation of the sun appearing to carry the planets onwards in then- course. That which is yery remarkable is, that just as the sun appears to turn the yarious planets around him, so do the yarious planets turn their satellites around them. If now we consider the improbability of eight primary planets, about sixty smaller planets, and upwards of a dozen satellites all follow- ing this rule ly chance^ we at once perceiye IN THE HEAYEXS. 51 that these movements must be obedient to a law. The following diagram will explain the joint movement of the sun and a planet, and will also show a curious fact connected with the earth's movement and the distance of the moon. S represents the sun, which turns round from A to B. M N is the earth's direction of movement. If now we suppose E the earth, about which 52 COMMON SIGHTS a circle is described with a radius of about two hundred and forty-five thousand miles, and then cause this circle to roll like a wheel around M N, then the earth would turn round just as often as it does every year, to perform its annual course : the radius of the small cu'cle is nearly the mean distance of the moon from the centre of the earth. Thus if we considered the earth the nave, and the moon's orbit the tire of a wheel, then this wheel would roll around the sun at their present distances, in as nearly as possible 365 days. From the experiments of various philosophers it has been shown that, when a magnet is made to rotate upon its axis, it will cause many sub- stances near it, as well as gases, to rotate also. It is not necessary that the substances should be themselves perceptibly magnetic; for clay and wood have been found to be thus in- fluenced. May it not be possible that the rotation of the sun causes in some way the rotation of the various planets ? and may we not have become acquainted with an effect only. IX THE HEAYEXS. 53 when we speak of grayity. and the haws of gravity ? The mdiyidiial who observed the effect of an electro-magnet,, might possibly at fii'st overlook the fact that the battery was the instrnment as well worthy of study as the piece of iron which attr-acted the various metals placed near it : for the more we can trace effects to other effects, the nearer we must be to causes. The Sim is spherical, and rotates upon an axis, and thus bears a strong likeness to the planets. A Cjuestion which naturally arises here is, whether the sun is entirely independent as regards its source of heat-giving power ; or is it connected by some subtle means vith another orb? Is the sun, in fact, a planet to some other sun ? and is our eaith, and are the other planets, but the satellites of our sun ? Vre have seen that there is good reason to beheve that the spots on the sim produce some effects of a magnetic and electric character upon our earth ; and we are by this fact pre- pared to believe that there are agencies at 54 COMMON SIGHTS work in the universe of a subtlety and power beyond our present knowledge or experience. Thus the sun may be influenced in a measure by some distant twinkling star, which is yet a mysterious link between our sun and other portions of creation. If there were an inhabitant on one of Nep- tune's satellites, he might not think much of the influence of our sun upon his primary planet,. and he might be sadly puzzled to ac- count for the variations in light and darkness which occurred. Some observers have supposed that the two hemispheres of the sun do not give an equal quantity of light. If this behef be a truth, it would give some probability to the supposition that the sun is not entirely independent ; for we might conclude that there was a summer and a winter on the sun, and thus that one hemisphere (the brightest) was then enjoying summer, and the other possessing winter. P1.4. 'Vjnr^.nt, BrO olcs ,llth . THE MOOIS^ SIX DAYS OLD. IN THE HEAYEXS. 55 CHAPTEE IV. THE MOOX. Next to the suu, the moon is the celestial object which attracts the greatest attention. From the earliest ages the moon has been con- sidered a mysterious body ; wielding influences over men's minds, and over the weather, and causing strange vagaries to be played by the otherwise orderly course of nature. It is not at all surprising that the moon should have been considered mysterious in an age when mystery was preferred to simplicity ; for her movements and condition, even in the present age, are subjects about which some un- certainty exists. To the casual observer, the moon's changes and movements appear hopelessly intricate ; but when we obtain a key to these, we find that 56 COMMON SIGHTS simplicity takes the place of apparent con- fusion ; and that the lunar machinery, like all Nature's works, is arranged upon the most beautiful and orderly system. The moon first appears like a thin crescent, and close to the sun. The side nearest to the sun is that which is illuminated. Soon after the sun has set the moon also disappears beneath that portion of the horizon near where the sun set. If the evening be fine and clear, not only will the thin bright crescent of the moon be visible, but also the whole round body, which appears of a pale-yellowish tint, and somewhat smaller than the bright crescent. The moon is a body which gives out little or no light from itself, but merely looks bright in consequence of its reflecting the sun's light. Thus, when it appears in the heavens as a thin crescent, this appearance arises from the greater part of the sun-lighted portion of the moon being invisible to us. The paler light of the remaining portion of IX THE HEAVENS. 57 the moon is due to the reflected light of the earth, which then shines on the moon just as does the full moon upon the earth. We must remember that, when a ball is shone upon, half the surface of that ball will always be lighted ; and, just as we stand with reference to the ball, so can we see the lighted portion as a thin crescent, a semicircle, or a circle. When we see the moon as a thin crescent, that part upon which the sun shines is only partly turned towards us, and the earth, the moon, and the sun are nearly in the same straight line. If we watch the new moon, we shall find that each night the crescent will appear larger and larger, until the bright portion is of a semi- circular shape. During these changes it will be found that the moon moves farther from the sun each night ; and, instead of setting imme- diately after the sun, as was the case when she was in the thin crescent form, she will now be nearly to the south when the sun is in the west. 58 COMMON SIGHTS When the moon is half enlightened, or rather when we see the half of the lighted part of the moon, then a line drawn from the sun to the moon vrill be at right angles to one drawn from the moon to the earth. The ancient astronomers were aware of this fact, and they suggested a yery ingenious method for determining the relative distance from the earth of the moon and the sun. They- Avatched until the moon appeared an exact semicircle : they then measured the number of degrees between the moon and the sun, and they thus had a right-angled triangle, as follows : — M was the moon, E the earth, and S the sun. The anoie S M E they knew must be a rio-ht angle ; the angle M E S they measured, and consequently they knew^ the proportional dis- m THE HExiYENS. 59 tance of M E and E S ; for the three angles of any plane triangle make 180^. Thus they could find the angle M S E. Then by rule of three — As the sine of the anole M S E Was to the distance M E, So was the sine of the angle EMS To the side E S ; and thus the proportion between M E, the moon's distance, and E S, the sun's distance, became known. There is sometimes a great difference between theory and practice, and so it proved with this problem ; for the ancients came to very dif- ferent conclusions, in connection with the re- lative distances of the sun and moon, from those which are accepted in the present day. The idea nevertheless was ingenious, however un- certain were the practical results. The enlightened portion of the moon will each night appear larger and larger, and she will move farther from the sun, until she is quite circular. At this period the earth, moon, 60 COMMON SIGHTS and sun are in a straight line, the moon being on one side of the earth, the sun on the other. When the moon is full, she rises at nearly the same time that the sun sets, and sets at the same time that the sun rises. The same changes take place duiing the decrease in apparent size of the moon that occurred during her increase, except that it will be the eastern side that is now illuminated, instead of the western. So that, if we stand facing the moon, we shall see the right-hand side illuminated dm^ing the time that she in- creases in brightness, and the left-hand side when she is decreasing. Just before sum^ise we may observe the moon like a thin crescent, just as we see her at times after sunset when she is new, the opposite side being now bright. The moon, like the sun, sometimes appears of a large size on the horizon, and of a deep red tint, and her colour and brilliancy vary considerably. These effects are most probably due to changes in the atmosphere of the earth. IX THE HEAVEXS. 61 When we know that it is the sun that causes the moon to seem bright, there is an appear- ance in the moon which at first sight is para- doxical. This is, that if we draw a straight line from the sun to the moon, the illuminated part of the latter does not at all times appear at right angles to the former, as it ought to do. This becomes most apparent when the moon is about half full, and is about south-east when the sun is south-west. The following sketch will show the appearance referred to. MOOx ^^&ru, Eo rizon . ^^^ This is due to the horizon being aiwarently a straight line, whereas it is really a curve ; and as we refer the line between the light and darkness on the moon to the horizon, this line appears not to be perpendicular to the former. All the celestial bodies appear to describe 62 COMMON SIGHTS circles in the lieayens, altliongh they may re- main stationary ; and thus any 'portion of the apparent course of a celestial body appears to be part of a circle. If the moon, instead of being a spherical body, were a long attenuated body, she would appear in the heavens like a bow. We can easily see how this would be, if we observe where the moon rises, and where she is at various times during the night. Then, if she were a long thin body, the various portions would extend in a curve from the eastern horizon to nearlv the south, much in the man- ner shown below. 1, 2, 3, 4, here represent the various positions of the moon at different times during the night. Then, if the moon were a long thin body, it would appear as sho^m by the Kne 1, 2, 3, 4. IX THE HEAYEXS. 63 This is the reason why the tails of comets most frequently appear curved.* If, however, a person were in the central portion of the earth when the moon passed dhectly overhead, this same line vrould appear to be straight, just as a bow would appear straight if held with the bow- string towards us. Thus a comet's tail might appear bent to an observer in the northern or southern portions of the earth, but quite straight to an observer near the central latitudes. The bendmg being dependent upon the direction of the comet's tail in the heavens in connection with the horizon. If the moon be observed dining several nights, it will be seen that her height above the horizon varies considerably^ Sometimes "^ It has been remarked by several observers that the tail of the great comet of 1861 Tvas straight, and that this was a peculiarity. The fact was that the appearance was dne to the position of the tail, which extended from ithe horizon to the zenith. K the tail had extended from east to west and over the equator, then to an observer in the north or south the tail would appear curved ; but if the tail were near the zenith — /. e., if an observer were at the equator, it would at the same time seem to him quite sti'aight. 64 COMMON SIGHTS slie rises and passes to the south with a less altitude than the sun has durins: midwinter. Then, in less than a fortnight, she will pass to the south with a greater height than has the sun duiing summer. The reason of this is, that the moon moves around the earth in about 27i ; days and thus, durmg the half of that period, a change in the altitude of the moon takes place, just in the same ihanner as a change in the sun's altitude occurs in six months. The following figure may aid to explain this fact. ^4r E represents the earth ; the direction of the north pole of w4iich is indicated in the sketch. A and B are two positions of the same observer on the earth's surface ; x and y represent two positions of the moon, so that, if x be the moon's place on any day, then fourteen days IN THE HEAVENS. 65 afterwards the moon will be in the position shown by y. To the observer when at B, the moon will appear very low down, and near the horizon ; but when he is at A, and the moon at y^ then she will appear nearly over his head. There are several other changes which occur in the apparent height of the moon, but these are beyond the range of the present book. We remarked that the moon moved round the earth in about 27^ days. This, however, is not the interval between two full moons or two new moons, &c. The period between two full moons is about 291 days. This difference arises from the fact that, wliilst the moon moves round the earth, the earth moves round the sun. If the earth stood still, then the moon would become full at intervals of 27^ days. Thus, in the following sketch, S is the sun, E the earth, and M N three positions of the moon, which at M is full, at half full, and at N invisible. If the earth remained at E, and F 66 COMMON SIGHTS the moon moved round from 31 to and to X, then the interyals between the Ml moons would be just equal to the time of the moon's passage round the earth. If, however (as is the case), the earth moves on to V, then the moon will have moved round the earth, and will have reached to Q in 27-^ days, but she wdll have to move on to R before she appears '' full," and it occupies her rather more than two days to move from Q to E. The shorter of these two j)eriods is called the sidereal revolution of the moon, the longer the synodic revolution. IN THE HEAYEXS. 67 In consequence of the earth turning round on its axis, we have an alternation of day and night ; and if there were an observer on the sun, every portion of the eartli would be visible to him once in twenty-four hours. The moon does not turn upon her axis in the same manner as does the earth, for only about one half of the moon has ever been seen by man. This arises from the fact that the moon turns round in exactly the same time that she moves roimd the earth. If we were to stick a sword into a large apple, hold the sword with the apple on the point at arm's length, and then move the sword around us, we should only observe one half of the apple, and the apple itself would not spin upon its axis like a top. Just so is it with the moon, which always turns one face towards our earth. In consequence of the moon revolving round the earth, she is of course lighted on all sides by the sun, and thus during about twenty-nine and a half of our davs the moon has one dav 68 COMMON SIGHTS and a night, so that her day is rather longer than fourteen of our own. If our earth were to move in a similar manner to the moon, only a little more than one half of the earth would ever see the sun, whilst the re- mainder would be in darkness, and thus there would be no evening and morning, and no alternation of day and night. Some singular ideas are forced upon us when we consider this subject, and find that in the Mosaic account of the earth's earlier histories, there was a period when there was darkness upon the face of the deep, for it appears by this, that the evening was, and the morning- was, aftei^ the first condition. It would be sin- gular if in the vast ages to come the terrestrial inhabitants were to find the moon bestirring herself, and turning on her axis like the earth. Yet this change cannot be pronounced impos- sible, in consequence of our utter inabihty to explain the cause of the rotation of a single planet in the system. The moon follows the same law in her revo- IN THE HEAVENS. 69 lution that the various planets follow ; viz., she moves round the earth in the same direction that the earth rotates : thus the earth appears as it were to drag the moon round her, just as the sun appears by his rotation to drag the planets around him. The moon, when examined with the naked eye, appears to present a smooth and regular surface. There are dark patches in various parts, which assume the form of a man's face, but there does not seem to be any great irre- gularities on the moon itself. When, however, we direct a telescope of moderate power to- wards the moon, a strange scene is presented to us; the curious face-like appearance disap- pears, and we observe a collection of light and dark patches, streaks of light or shade, circular lines, and all the varieties of a volcanic and mountainous district on earth. That portion of the moon which borders on the dark part is covered with long shadows, whilst here and there brilliant peaks shine against the dark background. Occasionally 70 COMMON SIGHTS two or three star-like objects become visible near the borders of the enlightened portions of the moon, as the sunlight is reflected from the most lofty mountain summits, which are illuminated before the less eleyated localities near them. Huge craters and long ravines, gentle slopes and clusters of mountains, all become visible with the aid of the telescope- The appearance presented by the moon's sur- face is like that of a vast volcanic district, where igneous action has only just ceased, and where the forces at work have been much greater than upon our earth. Some of the largest craters on earth are not one tenth as large as those on the moon. Thus Tene- riflfe scarcely exceeds nine miles in dia- meter, whereas a crater in the moon called Clavius measures about one hundred and forty miles. Some of these lunar craters are circular, whilst others are very much elongated. They are best seen when the moon is only partially lighted by the sun, and when consequently the IN THE HEAYEXS. il sides of the crater cast shadows upon the siir- roundino: hollow ofroimd. Mountains and yalleys, hills and dales, are observed on the moon ; but there does not appear to be any indication of large seas, or even water. Eecent observations have led to the belief that there is vegetation on the moon, at least at times, but this statement requhes confirmation. It is very easy to see, tiiat if we know the length of shadow which an object casts, and the angular position of the light, that we can ascertain the height of the object. This fact has led to the investigation of the heights of the mountains in the moon; and some very elaborate tables have been constructed, sho^^dng the altitude of the various mountains. There is, however, very little dependence to be placed upon these conclusions, however in- genious they may be, for it does not in the least follow that the hiohest mountaiDs should o cast the longest shadows ; and the various altitudes assumed for the lunar mountains 72 COMMON SIGHTS are calculated upon the supposition that they do. For instance, upon earth the Himalaya mountains are the highest. These mountains are not very abrupt in parts, but they slope gradually upwards, and therefore they would not, with the sun in any position, cast a very great shadow. And if we observed the earth from the moon, the Table Mountain, which rises abruptly, would cast a longer shadow than the Himalaya mountains, and w^ould therefore, upon the above assumption, be supposed much higher, whereas in reality it is not one-sixth the height. The length of shadow cast by a lunar moun- tain will merely give the elevation of that mountain above the surface immediately around it, but it will not give the relative altitude of the various mountains above a fixed datum. When we consider the preceding reasoning, it induces us to believe that the mountains in the moon are much higher than any on the earth, for some of the elevated peaks are found to be IN THE HEAVENS. 73 nearly twenty-fiye tliousand feet above the sur- face in tlieii' immediate neighbom^hood, and thus they may be several thousand feet more above the lowest gTOund. If it be a fact that the moon is not possessed of any seas or lakes, it appears only in accord- ance with terrestrial conditions that there should be yerj great irregularities on her sur- face ; for if the earth had no sea there would be some deep ravines and mighty peaks ex- posed to view in various places where the ocean now exists. The outline of the moon is somewhat jagged and irregular, but not to so great an extent as might be at first supposed. The approach to uniformity arises from the fact before men- tioned, that we should merely observe the pro- jection of certain peaks beyond the surrounding ground, and thus, although there would be irregularities in the outline, still these would not be so very marked. The surface of the moon appears to have been considerably disturbed, and torn by various 74 COMMON SIGHTS forces. The deep craters at once show this. There is, however, another action apparently at work, and which produces stars and rents, just as when the ice has been broken by a skater. These flaws appear to indicate that there has been, or is, some upheaving force going on in the lower strata of the moon, and which causes the surface to crack and separate at the lines of least resistance. In fact, there would be in the moon numerous flaws in the strata similar to the " faults " in the lower deposits of our earth. We have not to search far before we find a probable cause for the highly volcanic con- dition of the moon's surface. Any traveller v>^ho has passed a day upon the burning plains in tropical regions, when the sun at midday is in his zenith, and when he is exposed to the sun's rays only twelve or fourteen hours, can imagine the state in which the soil and air would be were the sun to remain twelve or fourteen days above the horizon. This is the condition of each portion of the moon's surface, which is exposed during about a fortnight to the con- IX THE HEAYEXS. 75 tinued rays of the sun, and then, during a like period, the sun is invisible. It is only reasonable to suppose that what- ever may be the condition of the lunar atmo- sphere, and the other agencies appertaining to her, still the sun causes heat upon her surface, and during his absence there must be cold. A very great alternation of climate, therefore, occurs upon the moon during every month, heat and cold being both very intense : and these great changes, and the long-continued action of the sun, it is highly probable would produce volcanic action, especially if just be- neath the lunar surface there are rocks con- taining sulphur, or other non-conducting matter. It has long been a subject of discussion whether there are any volcanoes now burning in the moon. Some observers have come to the conclusion that they have seen luminous points, which could not be accounted for in any other way than by supposing these to be active volcanoes. Other observers deny that there is any evidence to prove that volcanoes 76 COMMON SIGHTS are at present active, and that which indi- viduals have supposed to be a volcano, was merely an illuminated peak. In controversies of this description it must be borne in mind that no amount of negative evidence is sufficient to disprove one fact, and thus if half a dozen careful observers have seen appearances which may be fairly assumed to be active volcanoes, it matters but little whether half a hundred individuals have never seen anything of the kind. It certainly appears reasonable to suppose that there is igneous action going on upon the moon's surface, when we consider her appearance, and the amount of sun heat to which she is exposed. We ought to look for active volcanoes after the moon is full, as she has then been exposed to a continuance of sunlight for a long period : thus when the moon is south, at about 2 or 3 o'clock a.m., is the best time. If there be any very great changes occurring upon the moon's surface, these ought in the course of a few years to be discovered. Photo- IN THE HEAVENS. 77 graphy is an artist who neither flatters nor tells falsehoods, and now that a photograph of the moon can be taken, and when this photograph can be placed under a microscope, we may col- lect a variety of lunar portraits, which, handed down to posterity, may serve to clear up this otherwise questionable problem connected with the geology of the moon. It has been remarked that when the public are left to themselves, they will frequently, by a sort of intuition, come to correct conclusions upon even abstruse subjects. We must, how- ever, take care that we do not confound this sort of intuition with opinions which are the result of a bias being given to public opinion by self-elected authorities. The earliest almanacs invariably connected a change of weather with a change of moon, and thus a bias was given to public opinion which might not otherwise have expressed itself. There is to the loose reasoner something re- markably agreeable in the vagueness of the terms "change of weather" and "change of 78 COMMON SIGHTS moon." What does change of weather mean ? From wet to fine, from fine to wet; from cloudy to clear, from clear to cloudy ; from damp and foggy to dry and frosty ; from a cold north wind to a mild south wind ; from a nip- ping east to a soothing west \^ind ; from snow to rain, from thmider-storm to calmness ; from a hurricane to a gentle breeze — are all changes of weather. Then a change of moon, what is this ? First, the moon is invisible, then there is a new moon. This is a change. Then the moon is half lighted, then she is full, then she is half-lighted again, then invisible. Thus, once a week, the moon '^changes." Now it would be indeed strange if some change of weather, in some localities, did not occur at or about some of the periods when the moon changed. We have mentioned different localities, and this is an important consideration, for if we compare the weather in even various parts of England, we find but little uniformity at the same time. If the climate of Enoiand be com- IX THE HEAYEXS. 79 pared with that of the Continent, still greater differences will be found. Which locality, then, is to be taken as the one which is affected by the change of the moon ? In consequence of observations having been carried on in various places, different conclu- sions have been arrived at by different scien- tific men in connection with the influence of the moon on the weather. Thus observations car- ried on at Stutto-ard and Paris o'ave different results from those which were made at Poitevin. il. Gasparin found, according to M. Arago, that there was the least rain between the full moon and the last quarter, whereas at Stuttgard the least rain was found at the period of the new moon. From a consideration of the various facts collected by different experimentalists, it ap- pears that if the changes of the moon do pro- duce any influence upon the weather, the results of these influences do not cause so great a change, as the local conditions surroundins: different places. 80 COMMON SIGHTS We are upon tolerably safe ground when we assert that the moon causes some of the tidal changes upon earth, and that consequently she attracts the waters of the ocean. Granting this, we do not find it impossible to believe that when the atmosjDhere is imbued with a large amount of moisture, that she would attract the atmosphere in a manner somewhat analogous to that in which she attracts the ocean. When we have to consider attraction, we have a very subtle force to deal with, and conjecture must enter largely into the investigation, whilst posi- tive certainties cannot be obtained. Dealing- then merely with conjectm^e, it becomes a question whether, when the moon thus attracts the waters of the ocean or the atmosphere, she draws from either any of those elements of which water is composed. We find that attrac- tion will act at the distance of many millions of miles, and it is not, therefore, like any material forces with which we can deal. It might be then, that when the moon is thus attracting the ocean, she is. bv means of the IX THE HEAVENS. 81 subtle chemistry of nature, drawing from it some of the elements of which she herself is deficient, and thus she may be forming an atmosphere, or obtaining moisture which will, by the action of the sun's heat, enable her to produce an atmosphere. This action may be, according to human ideas, very slow ; still, if it exist, we should find our moon passing from its present hard granitic and volcanic state, into a condition which would admit of vegetable and animal life of a low order being created upon its surface ; and thus a geological change would be marked. Perhaps also this long sun period of fourteen days might, when the moon possessed an atmo- sphere, be suitable for the growth of plants which did not produce hard wood ; and thus ferns would predominate, which would cease to live immediately the sun ceased to shine upon them. Their fall would be probably attended by a deposit of snow, which another long day would melt, and thus growth of ferns might follow growth of ferns, and layer after layer of 82 COMMON SIGHTS vegetables might be deposited, which would eventually perhaps become the coal beds for those who were created upon the moon, when its youth had advanced towards maturity. In the absence of certainty we can only deal with conjecture. Another subject of discussion connected with the moon is, whether or not she possesses an atmosphere similar to the earth. There is reason to believe that if the moon possessed an atmosphere, then, when any stars passed the limbs of the moon, their shape and appearance would be considerably altered. As might be expected, phenomena of this description have been carefully watched ; and there are few in- dividuals provided with a telescope of even moderate power who have not observed seve- ral such transits. Some difference of opinion naturally exists as to whether the star or planet has shown any variation as the moon passed before it ; but the majority of observers agree in the belief that no change is produced. It is assumed that the atmosphere of the earth does IX THE HEAYEXS, 83 not extend beyond forty-fiye miles from the surface ; but this is merely an assumption. An atmosphere of a rarefied character may extend to any distance. In fact it is difficult to say to what extent the earth's atmosphere may ex- tend ; and it is possible that the moon may be within the radius of the earth's atmosphere ; and thus there may be a means whereby her volcanoes only smoulder, as it were ; whereas, if there were a more dense atmosphere, these would burst out into fierce flames. We should of course find no alteration in the appearance of a star as the moon passed it, if the moon were within our atmosphere, unless immediately about the moon, the air was much more dense. When we observe the incomplete or un- finished state of the moon, and then regard the present condition of our earth, it is difficult to avoid the conclusion that the moon is the younger of the two. There is an appearance about the moon's surface very similar to that which the earth must have presented during that early geological period, when granite or 84 COMMON SIGHTS gneiss were the surface soil, and when there were not yet conditions sufficiently favourable to organic life to admit of the existence of any beings of a higher type than a few worms or zoophytes. When we consider this probability? and when we regard creation from an expansive point of view, we are irresistibly struck with the singularity of the statement of Lucian and Ovid, who both inform us that the Arcadians asserted that their forefathers had inhabited the earth before it possessed a satellite. Some objectors, who are more ready to raise an objec- tion than to weigh the soundness of their argu- ments, have believed that they had exposed the absurdity of this statement when they said, *' Then the moon must have been a comet, and if so, what has become of its tailT This weak objection is so readily answered, that it is sm- prising that it was ever urged ; for we might remark that the moon, if an old comet, has done with its tail, just that which the comet of Encke has done with its tail ; for this short-period comet exhibits no tail, and when nearest the sun it IX THE HEATEXS. 85 has a diameter not one-tentli of that which it has when at its greatest distance. Thus the approximation of its particles appears to be connected with its distance from the snn ; but it does not necessarily follow that the moon was a comet : it might have been formed in several other ways. A statement such as that of Ovid is not to be hastily disposed of, either by ridicule or an off-hand objection; but probabihties must be weighed, and guesses should not take the place of facts. The distance of the moon is more readily obtained than is that of any other c-elestial body, in consequence of her nearness to the earth. Two locaKties situated in distant parts of the world are chosen as points for observation. The latitudes of these two stations being kno^m, the distance in angular measm^e of the moon, from the north pole and fi'om the south pole, may be obtained. Thus, if G and C were two points upon the earth's surface, such as Green- wich and the Cape, then the angTilar chstance 86 COMMON SIGHTS of the moon from the south pole of the heavens, added to the angular distance of the moon from the north pole of the heavens, will exceed 180'' by exactly the angle G M C. The distance in miles between G and C is known. The two sides M G and M C are so nearly equal as not to interfere greatly in the question, and thus the angles M G C and M C G are known, consequently the sides M C can be found by simple trigonometry. It will also be evident that to an observer at G, the lower portion of the moon might appear to just touch a star, wliilst the same star would appear at some distance from the moon to an observer at C. Hence another means is afforded for finding the distance of our satellite, which amounts to about two hundred and forty thou- sand miles ; a short distance when compared to lis THE HEAVEXS. 87 that of other celestial bodies, but still one suffi- ciently great to occupy an express train tra- velling at fifty miles an hour, rather more than three months to accomplish the journey. As soon as the distance of the moon is found, her size can be ascertained ; and she is quite small when compared to the earth; her diameter being only about two thousand one hundred and sixty miles. An eclipse of the moon lasts a much longer time than an eclipse of the sun, first, because the earth is larger than the moon, and secondly, because when the moon is eclipsed, both she and the earth are moving in the same direction, but when the sun is eclipsed, then the two are travelling in opposite directions. The following diagrams will explain this : Suppose S the sun and E the earth, which, with the moon, is travelling in the direction from A to B ; M the moon, during a solar eclipse, is travelling round the earth from M towards 0, and thus moves in one direction whilst the earth is moving in the other. During COMMON SIGHTS a lunar eclipse, however, the moon will be at Is, and will then be moving from N towards P, a course which at N is nearly the same as that ^\o F^. _M|t which the earth follows. Thus the moon re- mains some time longer in the earth's shadow, and consequently prolongs the lunar eclipse. To produce either a lunar or solar eclipse, it is evident that the earth, the moon, and the sun must be in the same straight line. In con- sequence of the moon moving around the earth in about twenty-nine and a half days, these three bodies must be twice during that period in nearly the same straight line. Thus it may appear at first sight singular that during every twenty-nine and a half days, there should not IN THE HEAVENS, 89 be an eclipse of the sun and moon. The fact however is, that the moon only crosses the actual path of the sun tvdce during her revolu- tion round the earth ; if therefore she does not cross this path either when she is full or invi- sible, then no eclipse can occur. There may be seventy eclipses observed in different parts of the world dming a period of eighteen years ; of these, forty-one are solar eclipses, and the remainder (twenty-nine) are lunar. In consequence of the proximity of the moon to the earth, eclipses of the sun may be seen in some parts of the earth as total eclipses, in other parts as partial, whilst in others the eclipse is invisible. In this respect an eclipse of the sun differs from a lunar eclipse. When- ever the moon can be seen above the horizon during the time of an eclipse, then also the phenomenon can be observed ; but it is not so with the sun, which, although visible at the same instant to two observers, may be partially eclipsed to the one but not to the other. The 90 COMMON SIGHTS reason of this may be understood from the fol- lowing diagram : Suppose S the sun, P the earth, and M the moon. An observer standing at upon the earth's surface, would see the moon in the direction of T, far above the sun ; therefore to the locality the sun would not appear to be eclipsed. The observer at P, however, would see the moon in the direction S ; that is directly between him and the sun, which would consequently be totally eclipsed. As the sun would not be eclipsed to the observer at O, whilst it would be totally hidden by the moon at the point P, it is evident that if observers were placed at various stations be- tween P and 0, [they would see the eclipse IX THE HEAYEXS. 91 nearly total, or partial, according as tliev ^Ye^e near to P or 0. T\lien the moon is eclipsed, the phenomenon is due to the earth's shadow, and this shadow will not alter its apparent position, although an observer may alter his. Thus a total eclipse of the moon will be a total eclipse at all places where the moon is above the horizon, and a partial eclipse ^vill be a partial eclipse. Thus there is no necessity to travel to different parts of the world to obtain a better view of a lunar, although it may be to see a solar echpse. If we take any particular locality upon the earth's surface, we shall find that more lunar eclipses are visible from that locality than there are solar, because the duration of a lunar eclipse is greater, and it is more likely to be visible than is a solar. Taking the whole world, how- ever, three eclipses of the sun will occur to two of the moon. The best time for observing the surface of the moon with a telescope is during the first quarter. She will then be visible ia the south- 92 C03IM0N SIGHTS western portion of the heavens as soon as the evening is sufficiently advanced to enable us to see her without difficulty. The sun is then shining upon the moon, so as to enable an inhabitant of the earth to see distinctly the shadows cast by the lunar craters. These cra- ters vary in size and form ; some are very large, being as much as one hundred and forty miles in diameter : many of them appear to have a small opening or aperture in the centre, which is surrounded by a ridge, or this appearance may be merely a peak in the centre of the crater. Even during one night a considerable change occm-s in the appearance of a crater, in consequence of the rise of the sun, as the shadow cast by the side of the mountain will decrease, fresh peaks become illuminated, and various irregular lines of hills appear to alter their form. Much of the beauty of con- trast produced by the variation of light and shade is lost when the sun shines nearly verti- cally upon any part of the moon ; thus the full moon is not so interesting an object for exami- ■wo2Mes. YmcenvBrods^IiiL 1. Craters on , liVIplioiiso kc. ' 7. lIa.iiro ly cii s . S-SouOi of Mooji . neaj^ Maic :viibiixm.. 8.Aj^ejmme^ 2. Craters West iS.Posidomas . . 9. lydio of jsppenn ines i 6 . Wes tborder of Mare lin bnum IX THE HEATEXS. 93 nation as is the same orb when about one-third of the illuminated surface is directed towards the earth. On Plate 5 are sketches of various portions of the moon's surface taken at different periods. These sketches have been made with a small but very good telescope, and may serve to show the great irregularities upon the face of our satellite. On Plate 4 is a diagram of the moon taken when she was partly visible. It will be seen from these that the lower and left-hand side of the moon are those parts which seem to be the most covered with craters. 94 COMMON SIGHTS CHAPTEE V. YENUS. The celestial object which appears at times the next largest to the moon, is the planet Venus. The brilliant white light reflected by this planet, and the fact of her being a morning or evening star only, and never visible during the middle of the night, caused considerable attention to be directed towards her from the earliest ages. One of the most important steps towards obtaining an interest in the movements and condition of the various celestial bodies, is to be able to tell whether the object which we see is a planet or a star, and also which of the planets it is that we may have seen. It is very rarely indeed that there can be any mistake in connection with the planets, and the slioiitest reflection will enable us to IN THE HEAVENS. 95 decide when we see a planet, whether it is Venus, or Mars, or any other. There are only two planets which appear of a large size, and which shine with a bright whitish light. These two are Yenus and Ju- piter. Mars, wliich sometimes appears as large as either of the former, always exhibits a bright red appearance, and cannot therefore be mistaken for them. In discerning therefore be- tween Venus and Jupiter, there might possibly be some confusion, but merely at a particular period. Venus is never very distant from the sun, and only rarely remains above the horizon more than an hour or two after the sun has set. She may rise also two or three hours before the sun. Thus she either immediately follows or precedes the sun. But Venus is never seen at midnight in any but very high latitudes north and south ; nor is she eve-r seen of an evening in that part of the heavens opposite to where the sun has gone down. Thus, if a very bril- liant white-looking celestial object is seen near 96 COMMON SIGHTS tlie western horizon in tlie evening shortly after sunset, or in the east just before sunrise, then this object is most probably Venus. If the planet Jupiter be in the same locality he will appear smaller and less brilliant, be- cause he will then be at a very great distance from the earth. Thus, even without any tele- scope, the planet Venus ought to be recognized ; but with the aid of one, no mistake can occur, for reasons which will be stated at a future page. The reason why Venus is never seen very far from the sun, is, because tliis planet moves around him in an orbit which is within that which the earth follows. Thus the earth never is between Venus and the sun, but Venus may be between the earth and the sun. In the following diagram S represents the position of the sun, W V the orbit of Venus, wliilst the largest circle represents the orbit of the earth. When Venus is at V and the earth at E, an observer on the earth would be carried round by the daily rotation from to P and IX THE HEAYEXS. 97 to Q. WTien this observer was at lie would be able to see Yenus at V whilst the sun was invisible ; then when he had been carried to P, the sun would be rising. Thus Venus would rise before the sun, and would consequently be a morning star. She would also set before the sun, and would not therefore be seen in the evenins:. 98 COMMON SIGHTS If Venus were at AV, then slie wonld rise after the sun, consequently from and P she would not be seen, on account of the sunlight; but when the observer had been carried round to Q, the sun would be invisible, but Yenus would be seen as an evening star. Venus moves round the sun in the same direction as does the earth. She, however, moves more quickly, and has a shorter distance to travel over to perform her annual journey round the sun. If we suppose that Venus is at V when the earth is at E, then as they both move in the direction shown by the arrows, the earth would arrive at about F w^hen Venus was at E, and she would dm^ing all this time remain a morning star. Thus this planet remains visible or invisible for a long period in conse- quence of the joint movement of the earth and herself. Venus is found to revolve around the sun in about 224 days 17 hours ; but she only returns to the same apparent position as regards the sun in 1 year, 3 months, and 29 days. That IX THE HEAYEXS. 99 is, in iiiteryals such as this she becomes an evening star or a morning star. The reason for this, as pointed out in the preceding dia- gram, is her motion combined with that of the earth. The distance of Yenus from the sun is found to be about sixty-eight million miles, the earth being about ninety-fiye millions. Thus at times Yenus comes within about twenty-flye million miles of the earth, a distance much less than that which eyer separates us from any other planet. Eiiowing the distance of Yenus from the earth we can readily obtain an ap- proximation to her size, about which, however, some slight uncertainty exists. It is generally admitted, however, that she is rather smaller than our earth, she being about seven thousand seven hundi-ed and eighty miles in diameter, whilst the earth is rather more than seven thousand nine hundred. Yenus, which appears like any other of the planets or stars when seen with the naked eye. presents a singular difference when she is ex- 100 COMMON SIGHTS amined with a telescope. A^Tien at her greatest angular distance from the sun, she appears to be half lighted, and thus exhibits a semicircle of brightness, just as does the moon at times. If she be seen in this condition dm-ing the evening, she will in a few weeks appear to approach the sun, and will seem each night larger and more brilliant. If she be examined with a telescope when she is brightest, the size of the illuminated portion will be about one- fom'th of the disc of the planet, but in conse- quence of her greater proximity, she aj)pears larger than when half illuminated. As she approaches the sun, the lighted portion becomes less and less, until at last she is lost in the sun's rays. Dm^ing a few days she is in- visible, and then reappears as a morning star, separates herself from the sun, and reaches about as far from him on the one side as she formerly did upon the other. When at the greatest apparent distance from the sun on the west side, she will rise about three hom^s before him, and if examined with a telesrope will be IX THE HEAVENS, 101 then found half illuminated on the side next to the sun. The phases of Venus, as these changes in appearance are termed, are not the only inte- resting facts reyealed when we dkect a tele- scope of moderate power towards her. For we find that she has an atmosphere like the earth, that there are appearances upon her wliich lead us to conclude that she has portions of her surface covered at times vith snow. We can see that she rotates upon an axis, and thus has an alternation of day and night, and also we know that she has a change of season. If from the sea-shore we observed two ships, each of which possessed a similar hull, masts, rigging, and sails, and if from each we observed smoke coming out of a chimney, these two ships would scarcely be more ahke than are the earth and the planet Venus. Each planet has an atmosphere, each is spherical, each has a day and night, a year, and a change of season. Thus when we examine Venus from the earth, 102 COMMON SIGHTS it is almost like looking at our owii planet from space. When speaking of the moon, we pointed out the fact of the whole body of the moon being visible when only a slight crescent was illu- minated by the sun; and this effect, it is believed, can be explained by supposing that the earth shines upon the moon. It is singular, however, that the same phenomenon has been observed upon Venus, the whole of whose surface has been distinctly seen when only a small portion has been illuminated by the sun. It admits of question whether the reflected light given by the earth would be sufficient to produce this observed effect on a planet as distant as Venus. In consequence of the orbit of the earth being outside that of Venus, our planet would give a much brighter light upon Venus than she ever gives to us, because the earth when nearest to her would appear ^^fuU," whereas she is only seen by us as a partially illuminated body. Thus the mliy light of Venus might be due to the earth's light re- IN THE HEAVENS. 103 fleeted on to her sm^face. It is not impossible, however, that the rotation of a planet upon its axis may jDroduce light in some way ; and thus Venus and all the other primary planets may give out a faint Kght, independent of that which they reflect from the sun. When ex- amining the system of Jupiter, we will again refer to tliis conjectm^e. That portion of Venus wliich is nearest to the sun, is found to be much more brilliant than the central part, where the light and shade almost meet. This is a natural consequence of the spherical form of the planet, just as the midday light on earth is gTeater than that in early morning, and the sunlight in equa- torial regions more powerful than in high lati- tudes. There is an additional obscuration of light upon Venus, which has led to the conclusion that she is surrounded by a highly refractive or dense atmosphere ; a condition which it is not improbable has been produced by her great annual chanR^e of climate. 104 COMMON SIGHTS The surface of Venus is covered with darkish spots of a deKcate character, and they occupy the greater portion of her diameter. Sometimes bright spots are observed upon various parts of her surface, or her atmosphere. These, however, have enabled astronomers to decide, that she rotates upon her axis, in a period of about twenty-three hours and tv/enty-one minutes.- Thus her day is rather shorter than the terrestrial day. The method of discovering the time of a planet's rotation is to watch for some remark- able spot to appear upon the planet, and to correctly fix the relative position of this spot ; then in some period either gTeater or less than twenty-four hours the spot will appear to have moved round the planet, and to have regained its first position. Some doubt might, however, exist, whether the spot had moved round only once, or whether two rotations or more had occurred during the intervals of observation. This question, however, may be settled if we observe the change which takes place in the IX THE HEAYEXS. 105 position of the spot during an hour or two^ for we can then estimate about the rate of rotation, and are not likely to make any very gTeat mistake or to confound a double with a single rotation. In addition to the rate of rotation, another interesting fact is ascertained by an examina- tion of the spots upon Venus, viz., we can find the relative changes which occur in the sun's altitude dmino' the Venus vear. This chano'e is found to be very great, and is of sufficient interest to attract special notice. If we examined from space the rotation of the earth during the two periods of summer and winter, we should find that the rotation took place at such an angle in connection with the position of the sun, that all localities within twenty-thi'ee degrees and a haK of one of the poles were durino; the twentv-four hours shone upon by the sun. If, however, we ex- amine Venus under similar conditions, we find that all localities within about seventy-five de- gi^ees of one of the poles are shone upon by 106 COMMON SIGHTS the sun during tlie twenty-four lioui^s. The course of the spots upon the earth and Yenus may be better understood by the following figTires. Earth. Venus. Venus. Earth. ^^ " .^^S::^ 3 __. -— _j^ ^'- ^ :-- - -Sto ^^^^^M- (iUA^J ^^^^^^ Ij 2, 3, show the direction pursued by a spot on the earth and on Venus. When, there- fore, we remember that the planet revolves round the sun, and thus turns towards it in summer that pole which was turned away from it in winter, we shall see that gTeat variations will occur in the two seasons in consequence of the variations in altitude of the sun above the horizon. To fully understand these changes we will suppose ourselves transferred to the planet Venus, and to a locality exactly simi- larly situated to England upon this earth. Here then we stand upon the sm-face of an- other world,^ which may or may not present IN THE HEAVENS. 107 very singular variations from oiu' own, — who shall say? We commmence our observations at that 23eriocl when the sun is over the equator, in the spring of the year, a date corresponding to the 21st pi March upon earth. Instead of that gradual advance from spring to summer which terrestrial beings observe, we in Venus find that the summer comes with a rush, as it were. On earth it takes three months for the sun to pass from its spring altitude to its summer, and even then it is not nearly over- head to people in England. Thirty days after the sun crossed the equator of Yenus, it would at midday be dh^ectly overhead to a locality similarly situated to England, Upon earth the only places where the sun is seen directly overhead is within tropical re- gions, that is, in latitudes not exceeding twenty- three and a half degrees. On earth, however, in those latitudes, the sun only remains about twelve or thhteen hom-s at a time above the horizon, and thus the intervals of sunlio-ht and 108 COMMON SIGHTS darkness are equally cliyicled ; the intense heat of the day disperses itself in a measure during the nighty and heavy dews moisten the ground, and thus enable the inhabitants to endure the midday heat of the morrow. This is not, however, the condition of Venus in the regions similarly situated to England. There the sun, as we have said, is vertical at midday, but it then passes obliquely to the western horizon, glides down to the north, just touches the northern horizon, and returns again to the zenith of our locality. Thus in about forty days after the sun has crossed the equator it would be vertical at midday, and would not set at midnight, and twenty-fom^ hours of sunlight would have to be endured if England were situated on Venus. From this date the sun would not set during the twenty-four hours, but would each night rise higher above the northern horizon, until in about fifty-six days it would daily describe a small circle in the heavens, the midday light IN THE HEAVEXS. 109 of the siin being about equal to that of our Slimmer sun, and the michiight sim il ar to that of spring. Thus for about thiity-two days and nights the sun would not set. On earth we can see the midnight sun if we travel into high latitudes, but we cannot see such a sight as a midday vertical sun and a midnight sun during twenty-four hours ; nor can we do more than imagine the intense heat which would be produced by such conditions as those which exist in Venus. From the period when the sun described its small diurnal cncle in the heavens until it again passed the zenith at midday, and touched the northern horizon at midnight, there would ela]3se about thirty-two days. The retreat of the sim would be as rapid as its advance. In one hundred and thirteen days the autumn position would be reached, and the sun would at midday be no higher than he is on earth at the same period. Just as the summer approached rapidly, so 110 COMMON SIGHTS would the milter, and in about twenty-eight days from the period when the sun was in the position corresponding to the autumn altitude in England on earth, he would be lost sight of in the same locality in Venus. A long period of some fifty days and nights would now elapse, dming which the sun would be invisible, and those very localities which were so lately ex- posed to an ultra-tropical summer would now endure an arctic wmter. There is now no light save that of the stars, and hence the cold would be as intense as was the heat. In 226 days the sun again returns to the spring position, and the yearly changes on Venus have been accomplished. These are strange conditions to be going on in a planet so near our own ; and it is difficult to avoid reflecting upon the changes which must be produced thereby. Each year an arctic winter, and a tropical summer, will alternate from her poles to within about fi.fteen degrees of latitude from her equator. IN THE HEAYEXS. Ill It would thus take some time for terrestrial beings to become acclimatized in Venus ; but who can say whether the creatures which exist upon her may not occasionally suffer from these very changes ? In her equatorial regions there may be troops of giant mammoths, which, attracted by the scent of the rapidly growing vegetation, are travelling northwards, as the sun in its northward course vivifies the face of the country. Onward they stalk, farther and farther, revelling in the shade of trees which the sun's heat has produced. During a hundred days these herds track far away from the equator, and enter the now glowing lands of the north. The sun performs its daily circles, but is again returning south, and the air begins to feel chill, and darkness at midnight warns the ancient bulls that it is time to migrate. Some members of the herds have strayed away however; their fate is sealed, for the country which but lately glowed with sun-heat 112 COMMON SIGHTS and was covered with succulent vegetation, is now a dark, bleak, snow-covered wilderness ; the water is frozen^ the vegetation withered, and the mammoth, crunching the dried branches, is forced to yield its life, unable to procure water, and incapable of sustaining the intense cold which penetrates even through its wool-covered hide. Many a monster might thus perishy and his bones would cumber the soil. Another season of heat, however, would shortly retm-n, — the snow would be rapidly melted, the pent-up streams thawed, and torrents of water thus produced would flood the country, carrying stones, sand, and icebergs with their burdens of boulders into strange regions, whilst the mammoth would be borne with the current and deposited amidst a mass of debris, near some watercourse, from which, centuries afterwards, when the planet's condition had changed, some geologist might exhume him, and speculate upon the cause which had produced such destruction amongst his fellows. IN THE HEAVENS. 113 There again is a mass of rock which is an- nually exposed to a process similar to that said to have been adopted by Hannibal when he crossed the Alps. A vertical sun raises this rock to a great heat during an uninterrupted period of several weeks, then the sun's absence exposes it to very great cold ; a change which w^ould probably cause the rock to split and separate, thus liberating large masses, which would be each year subjected to the action of the torrents, and which probably at length would become frozen into icebergs, and transported as boulders to distant plains. Owing to the annual alternations of climate in Venus, there must be glaciers and moraines, even vipon moderate elevations, in all localities down to within about twenty degrees of her equator. Not only would these glaciers exist upon hills where they do not at present upon earth, but they would be found to produce effects more powerful than any which we can observe ; for the effect of .the vertical sun iii summer oyer regions covered with snow would be very I 114 COMMON SIGHTS powerful. If our polar regions were subjected during a couple of months to a nearly vertical sun, the ice in those latitudes would be liberated, and w^ould be floated by the earth's rotation down towards the equator. Thus a whole fleet would be sent annually from the poles. In Venus the arctic ch'cle reaches to within about fifteen degrees of the equator ; and therefore nearly all localities, to the north of this, would be covered with drift and water-worn materials each year. Thus, whatever other local circumstances may affect Venus, stiU the sudden change from a vertical sun to no sun at all, must produce these alternations of climate, and probably that planet may be now passing through her glacial epoch. An examination of the mountains in Venus leads to the conclusion that they are much higher than any at present on earth. It ap- pears that they in some instances are as much as a hundred and forty-fom^ thousand feet above the ground around them. Thus these mountains IN THE HEAVENS, 115 are twenty-seven miles in height, while those upon earth do not exceed five miles. It is not impro- bable, however, that the great change of climate which we have spoken of as occmTing on Venus, may, in thousands of years, so rend and crack the elevated rocks as to produce greater uniformity of surface. At present, however, her mountains are enormous. It has long been a question whether Yenus possesses a satellite. It was stated by some of the earlier continental astronomers that they had distinctly seen one attending her; and some even went so far as to give the period of revolution of the supposed satellite. Modern observers, however, have not admitted the truth of these statements. This is a subject well suited to the inquuy of amatem-s ; for a good eye, a good telescope, and a little perseverance are all the requisites for investigation. As far as the matter has gone, the evidence is decidedly in favom- of Venus having an attendant ; which may, however, be liable to great variations in brightness, just as are the satellites of Jupiter. 116 COMMON SIGHTS Not only as regards her proximity and phases, but for many other reasons, our nearest neighbour Venus is an object of interest, and is well worthy of telescopic investigation. IN THE HEAVENS. 117 CHAPTER VI. JUPITEE. Almost rivalling Venus in brilliancy and apparent size, Jupiter is the next object to which we shall dii^ect our attention. This planet shines with a pale light, and is at all times remarkably brilliant, but most so when he is in the south at midnight, because then he is nearest to the earth. Jupiter is by far the largest planet in the system, and exceeds the earth in size as much as the eg'R' of an ostrich exceeds that of a sparrow; he being nearly ninety thousand miles in diameter^ whilst the earth is less than eight thousand. His distance from the sun is very gTcat, and his year a long one ; the first being four hundred and eighty- five millions of miles, and the latter nearly twelve of om' years. Thus Jupiter can never be 118 COMMON SIGHTS nearer to the earth than about four hundred million miles. Jupiter. The receptability of ligM of tHs planet must be very great, for he appears nearly, if not quite, as bright to us as does Venus ; yet the one throws his reflected light four hundred milUon miles and the other only about sixty million, and Jupiter is more than seven times as far from the sun as is Venus. IX THE HEAVENS. 119 Jupiter may be seen at any time of niglit, in consequence of his orbit, or course, being out- side that of the earth. From his large size and great brilKancy he is not likely to be mistaken for any other planet or star, unless it be the Dog-Star, called also Sirius ; but as the position of Sii'ius will be pointed out at a future page, even this mistake ought not to occur. However much we may be accustomed to deal with figures, we still fail to realize the great distances of the celestial bodies, and hence the vastness of the universe, unless we are more forcibly reminded of these distances by some comparison with terrestrial objects. Thus we may better comprehend the distance of Jupiter from the earth, when we find that if an express train, travelling continually, started from the earth towards Jupiter when he was at the shortest distance from us, it would occupy more than nine hundred years to reach him, although it travelled at the rate of fiftv miles an hour. Jupiter will always be visible during nearly 120 COMMON SIGHTS Dine months in the year, the period when he is invisible is when he is behind the sun. When first observed as a morning star he is not very brilKant, nor does he appear so large as he will when he is a midnight star. If when Jupiter is first observed as a morn- ing star, we notice the stars which appear to be close to him, we shall find that each morn- ino' he will when he rises be a little more to the east of these stars ; that is, he will appear to have moved to the left of the stars near him. This change in his apparent position will con- tinue for several days, after which he will gradually slacken the rate of his movement, and will then not appear to change his place amongst the fixed stars. After remaining stationary during two or three days, he will then appear to move in the contrary direction, that is to the right, and he will continue this motion for some months. He vvill then be- come stationary, and will again move to the left. These apparent changes of position, in a IN THE HEAVE:NiS. 121 remarkable celestial body such as Jupiter, caused tlie ancients to direct tbeir attention particularly to these " wanderers/' as they called the planets. The movements of the planets ap23eared to them, however, hopelessly intricate ; and probably even to modern observers, who have never devoted any great attention to tlie details of the celestial worlds, the above ex- planation may appear to indicate that intricacy is one paramount obstacle to thoroughly under- standino- the motions of the different celestial bodies. A little sketch may often do away with the apparent confusion of a description ; and such, we believe, will be the result in the present case if the following diagram be examined. The orbit of Jupiter is represented by the circle J K L ; that of the earth by the circle E F G; the sun is shown at S, and three stars are represented at B A C. The earth we will suppose to be situated at E, and Jupiter at J. Jupiter would now appear from the earth close to the star A, w^hich, however, is 122 CO^OIOX SIGHTS infinitely farther off than is Jupiter, but the two would appear close together in the sky. In about four months the earth would have moved to F, and Jupiter to K, whilst the fixed stars ABC would not have altered their positions. AATien the earth was at F and Jupiter at K, he would appear close to the star C, and there- fore he would seem to have moved, as regards the stars, to the left. In about three or four months from the last period, the earth would IN THE HEAVENS. 123 have readied G-, and Jupiter would be at L. Jupiter would now appear to have moved to the right of the star C, and to be close to the star B. Thus we have &st an apparent movement to the left ; then Jupiter is stationary ; then he appears to move to the right; then he is stationary again; and lastly, he seems to be moving to the left, when he is hidden by the sun's light. All these apparent changes in position of this planet are due to the jomt movement in the same direction round the sun of the earth and the planet. AATien Jupiter, or any other planet, moves from the right tovrards the left, that is from west to east, his motion is said to be " direct^' because this is the direction in which the sun appears to move amongst the stars during the year. When the planet travels in the opposite direction, its motion is said to be " retrograder Jupiter occupies a period of four thousand three hundred and thirty-two days to travel round the sun, and thus the Jovian year is 124 COMMON SIGHTS equal to eleven years and three months of our time. A Jovian gentleman, therefore, who was six years old ought to be thinking of retiring into private life, whilst a lad in the same planet, aged one year and a half, ought to be starting in some profession. To circumnavigate the planet Jupiter it would be necessary to travel no less than two hundred and eighty thousand miles, a distance greater than twenty-two voyages to Australia. Fontenelle, in his ^ Plurality of Worlds,' de- scribes very humorously the supposed con- ditions upon Jupiter, The countess says, " ' Pray tell me, if the earth be so little in comparison of Jupiter, whether his inhabitants do discover us ?' ^ Indeed I believe not,' says I ; 'for if we appear to him ninety times less than he appears to us, judge you if there appears any possibility ; yet this we may reasonably conjecture, that there are astronomers in Jupiter, who, after they have made most curious telescopes, and taken the clearest nights for then- observations, may have discovered a little planet in the IN THE HEAVENS. 125 heayens, which they never saw before : if they publish their discovery, most people Imow not what they mean, or laugh at them for fools ; nay, the philosophers themselves will not be- lieve them, for fear of destroying theii' own opinions. Yet some few may be a little cm^ious ; they continue their observations, discover the little planet again, and are now assured it is no vision ; then they conclude it has a motion round the sun, and after a thousand observa- tions, find that it completes this motion in a year ; and at last (thanks to the learned) they know in Jupiter that our earth is a world ; everybody runs to see it at the end of a telescope, though so little that it is scarcely discoverable.' " ' It must be pleasant,' says she, ' to see the astronomers of both planets levelling their tubes at one another, and mutually asking what world is that ? What people inhabit it ?' ' iSTot so fast either,' replied I ; ' for though they may from Jupiter discover our earth, yet they may not know us ; that is, they may not in the least suspect it is inhabited; and should any one 126 COMMON SIGHTS there chance to have such a fancy, he might be sufficiently ridiculed, if not prosecuted for it.' " If we were to trace a line in the heavens where the sun each year moves amongst the fixed stars, we should fijid that Jupiter is never very far from this line. He is at times just a little above, and at others equally below this line ; his greatest variation from it being rather more than twice the apparent diameter of the sun. Upon directing a telescope of even moderate powers towards Jupiter, he at once loses the star-like appearance which he exhibits when seen with the naked eye, and shows a round bright disc. Immediately in his neighbour- hood there will be seen four, or fewer, little bright bodies, which exhibit a constant light, differing slightly from that of a star. If these bodies be looked at occasionally during an hour or so, they will be found to have altered their relative positions as regards the planet and themselves. When a telescope is used with a high magni- IN THE HEAYENS. 127 fying power, Jupiter appears nearly as large as does the moon ; and tlie satellites, as the small attendant bodies prove to be, also show a diameter, and other interesting phenomena. AVe will first speak of the planet as he is seen by the aid of a powerful telescope, and secondly, of the satellites. One of the first facts connected with Jupiter, and revealed by the telescope, is, that like the earth, he turns upon his axis, and thus possesses a day and night. An examination of several spots upon his surface shows that the rate at which this large planet turns round exceeds by far that of the earth. The duration of the Jovian day and night is about nine hours and fifty-six minutes ; and thus these periods of light and darkness are nearly " watch and watch about," as on board ship. In consequence of the shortness of the Jovian day and night, there are upwards of ten thousand four hundred days in each year, and the various bodies on his equator are carried over a space of upwards of twenty-eight thousand miles per hour. 128 commo:n^ sights It is supposed that if the earth were to spin round with a velocity equal to the above, the various objects on the surface would be sent flying into space ; such an" assumption, however, is only a guess, and it is probable that the same force which causes this rapid rotation on Jupiter also causes other conditions which keep matters in order. Some amusing speculations have been made as to the supposed height which a cat might jump upon the surface of Jupiter, in conse- quence of this rapid rotation : of course by the aid of a few preliminary but important sup- positions, it can be proved that the leap of the cat would be enormous. So also might we find on earth, by certain theories, how much higher v>'e ought to jump at the equator than at the northern regions ; and thus the crafty foxhunter, by occupying the more equatorial portion of the field, might overcome obstacles which would effectually "pound*' his less scientific friends. As conjectures these theories are amusing, but as facts they are not very iX THE HEAYEXS. 129 valuable, for we know not as yet the causes of grayity, of a planet's rotation, nor of any of those effects which bear upon the question : and hence we cannot yentm^e to predict the result which might occur by an assumed change of conditions ; for we are but upon the sm-faee of a law, where we see its effects only, but know not the successions of effects which intervene between the great First Cause and that which our senses enable us to comprehend. The various marks upon Jupiter atlbrd a means whereby the changes in his seasons can be known. These chano'es are verv slight : and thus a singTilar difference exists between the climatology of this planet and that of Venus. The Jovian world has scarcely any change of season, provided that the variation in the sun's altitude is the only cause of change; for the difference between the summer and winter alti- tude of the sun is less than seven degrees, whereas on om- earth this difference amounts to nearly forty-seven degrees. The equatorial regions of Jupiter must therefore be much K 130 COMMON SIGHTS hotter than regions either to the north or south, whilst his polar regions are either eternally frozen, or upon the verge of a frost. There may be, and probably are, conditions upon that planet which fit it for the residence of beings possessed of senses perhaps higher than those on this world. It would appear to follow as natural, that the central portion of Jupiter should appear much brighter, than either the northern or southern regions, for the first locality receives the ver- tical, whilst the other receives the oblique rays of the sun. This conclusion agrees with obser- vation, which indicates a brightness in the central portions nearly double that of the ex- treme northern and southern regions. In addition to the spots which serve to indi- cate the rate of rotation, there also exist on Jupiter several singular dark and light streaks, called " helts^ These belts are all parallel to each other, and run across the planet in the same direction as his equator ; that is, they all lie across him from east to west. IX THE HEATEXS. 131 There have been instances recorded when there were no belts seem upon Jupiter, and yet at the same time clouds were visible in his atmosphere. Thus the belts change their a23- pearance, or yanish. They also seem at times to be brighter than the surface of Jupiter, or darker, according to chcumstances. There is usually seen a brig:ht central belt, bordered bv two darker lines; but it is singular that these do not appear to extend quite to the margin of the planet. WTiat these belts are is a matter of conjec- ture. It has been suggested that they are the effects of strong trade winds, or of lone tracks of fluid somewhat similar to water : but nothing satisfactory is yet kno^Mi, and the belts of Jupiter remain subjects for speculation and observation. Of late years attention has been di^awn to several bright spots upon Jupiter. During the years 1850 and 1857 some notice was taken of this phenomenon, and considerable interest has been excited therebv. Like the belts, how- 132 COMMON SIGHTS ever, these spots are mysterious, and they may serve to remind us how little we yet know of the laws which govern the universe and pro- duce changes in the various A^'orlds ; for not only are the spots on the sun mysteries, but the rapid rotation of Jupiter, his belts and bright spots, the ring of Saturn, and the purpose for which comets come, and a host of other phenomena, remain for future generations to explain. We may boast of being able to fore- tell for an immense period the time when an eclipse will happen, but we cannot predict the state of weather for even a week, and scarcely for twelve hours : yet as far as the convenience and benefit of society is concerned, the latter is the more likely to be practically useful. When we look back, and consider the advance w^hich has been made in science within a few cen- turies, we may even hope that the state of weather will eventually be predicted, with at least some foundation upon truth ; and perhaps, when the means of prediction have been dis- covered, we shall stand and wonder, lost in IX THE HEAVENS. 133 amazement how such a simple law was so long overlooked by our predecessors. During the autumn of 1857, when observing Jupiter with a telescope of moderate power, I noticed a singular appearance both above and below his poles. From the extremi- ties of the axis there were two streams of bright hght, in appearance like the tail of a comet, chverging as they receded from the planet, and plainly visible to a fhstance of ten diameters in both du-ections. The light ap- peared to vary in brightness and extent, and the phenomenon was very like an aurora. I &st supposed that this appearance was due to some defect in the object glass, but having ele- vated the telescope so as to be well clear of the light of Jupiter, I used the slow-motion screw to move the axis of the telescope across the observed light. Having performed this operation several times, and finding exactly the same appearance, I concluded that the phe- nomenon was connected with the planet Jupiter, 134 COMMON SIGHTS and not mth the telescope. Fortunately two friends came the same evening to the observa- tory, and upon looking through the telescope at Jupiter, they observed the same appearance ; although when we directed the instrument to a star of the first magnitude, no such effect was visible. The night was one of the clearest and best suited for observation that I have ever seen. A few nights after, the atmosphere was again suitable for delicate observations, and Jupiter was re-examined. Instead of per- ceiving the aurora-hke lights from the poles, there now a,ppeared a much more feeble, but still a similar light on each side of the equator, and consequently at right angles to the former. These appearances are sufficiently remarkable to be recorded. It may be a question for consideration whether a very brilliant au-rora on earth might not be seen, if there were an observer with a good telescope upon Mercury or Venus ; IN THE HEAYEXS. 135 and the phenomenon obseryecl upon Jupiter bore a strong resemblance to this terrestrial paradox. How TO FIXD JUPITEE UNTIL 1872. December, March, June and September, show the positions of the earth at these periods ; 1871 ^872 1S70 /1861 pher's Positions until 1872. 1869^ the dates 1861, 1862, etc., show the positions of Jupiter at those dates. Remember that the 136 C03IM0N SIGHTS sun is south at noon, and that the earth tin^ns round as shown by the small arrows. Jupiter's position may then be found at any time and season. In June 1861 the sun will be south at noon, and Jupiter (see 1861, fig.) will be south shortly after the sun. Thus Jupiter follows the sun, and will be visible for a short period above the horizon just where the sun has set. Where will Jupiter be seen at 6 o'clock p.m. in March 1862 ? The sun being south at noon, then at 6 p.m. in March the south would be in the direction S, therefore Jupiter (see 1862) would be in the east. WTiere will Jupiter be in September, 1869, at midnight ? The sun being south at noon, the south t\i11 be in the direction 1868 at midnight, and Jupiter will be seen to the east of south. In April, 1869, Jupiter would be invisible, because behind the sun. I^' THE HEATEXS. 137 In December 1870, at 11 p.3I., Jupiter would be seen to the south. Thus, by remembering that east is to the left of south, west to the right, and that the celes- tial bodies move fi'om east to west each night, we may always Iniow whether Jupiter will become yisible during the night, or where he is to be seen at any hom\ Jupiter is attended by foiu' moons, which are from two to three thousand miles in diameter ; the satellite next but one to the planet being the smallest, and the third satellite being the largest. Like the rotation of Jupiter, the revo- lution of these moons is very rapid; the &st satellite, although at a distance of two hundred and sixty thousand miles fi'om Jupiter, yet revolves round him in about forty-two and a half hours. The most distant satellite revolves round Jupiter in less than seventeen days, although it is more than a million miles from him. These satellites move round Jupiter; and 138 COMMON SIGHTS appear from his surface to trace in the heavens almost the same course that is passed over by the sun dm^ing a Jovian year. Thus during each revolution of the satellites they will eclipse the sun, and will also be eclipsed themselves. The fourth, or most distant satellite, is the only one which at times passes round Jupiter without eclipsing the sun, or being itself eclipsed by him. In consequence of the rapid revolution of these moons, and the position of the orbit in which they move, the inhabitants of Jupiter will witness upwards of eight thousand eclipses during their year. It is quite possible for the four moons to be visible at the same time in the heavens from Jupiter during the night. The first satellite would a23pear about the same size that our moon appears to us : the others would not be such prominent objects ; still they ought to appear larger than any celestial object which we can see except the moon. The rapid and variable rate of movement of these moons IX THE HEAYEXS. 139 must aftorcl the Jovian astronomers ample opportunities for finding their longitncle ; and the eclijDses of the sim and of the satellites must enable them to keep then- lunar tables in order, supposing that they have not yet discovered the cause of a planet's move- ments, or that they are independent of observ- ations. The echpses of Jupiter's satelhtes, their shadows passing over his surface, they them- selves being hidden, or •'•' occulted " as it is called, by him, and theh^ passage across his surface, aftord the means of finding the time shown by a clock at Greenwich, although an individual may be in any part of the world. In a publication called the ' Xautical Al- manac,'* and at about the 500th page, the date and time of the various phenomena are re- corded. These calculations are made for two years in advance, so that a traveller may take this publication with him to any part of the world. '^ Price 2s. Gd. 140 COMMON SIGHTS The following is the tabular arrangement adopted in the work referred to : — FEBEUARY. d. h. m. s. I. Oe. D. 1 21 23 I. Ec. R. 2 53 18-5 I. Tr. I. 18 36 II. Oc. D. 18 44 [I. Oc.D. 19 32 I. Sh. I. 19 56 I. Tr. E. 20 49 II. Oc. E. 21 20 *^* The abbreviations denote as foUows : — Ec. Eclipse. Oc. Occultation. Tr. Transit of SateUite. Sh. Transit of Shadow. D. Disappearance. K. Reappearance. I. Ingress. E. Egress. The year is of course indicated upon the back of the publication ; the month is shown as above, " February." The I. Oc. D. means that the 1st satellite is occulted and disappears behind Jupiter. The time of this occurrence is indicated by the 1 d. 21 hrs. 23 min. ; that is, at 21 hours 23 minutes past the midday of the IN THE HEAVENS. 141 1st of February, Greenwich time, the first satellite would disappear. The most conve- nient time for observing these phenomena is when Jupiter is found in the south at mid- night, because then he is nearest to the earth. The time of an eclipse or occupation would then be about 12 hours after noon, and indi- cated thus : Id. 12 h. m. s. ; that is, the first day a phenomenon would occur at 12, mid- night. It is of the greatest use to be able to tell the Greenwich time when at different parts of the world ; and it is even interesting in out-of-the- way country places to be able to set om^ clocks by the aid of a satellite, distant from us at least four hundred million miles. The four moons of Jupiter would appear a most singular and interesting sight to a terres- trial astronomer, as they rapidly traversed the sky of the Jovian world. Our one moon, when full, is a glorious object, especially when viewed through the transparent medium of a tropical atmosphere. But the sight of sights must be 142 COMMON SIGHTS the planet Jupiter seen from his first satellite. From this satellite the planet Jupiter could be seen to exhibit phases similar to those of our moon. Instead, however, of appearing a small body, like our satellite, Jupiter would appear a huge sphere, measuring in diameter more than thirty-eight times the diameter of our moon. Such a splendid body must, we should conceiye, when illuminated by the sun, cause the re- flected light cast upon the satellites to be nearly equal to the sunlight. Our telescopes, how- ever, do not clearly show that the side of the satellites nearest to Jupiter is much brighter than the side away from him, although in the first case there is the joint light of the sun and Jupiter, whilst in the second case there is the sunlight only. Thus it is evident that in spite of the distance of the sun, its means of light- ing the various worlds are such that Jupiter and his satellites are as brilliant as any bodies in the system ; and hence we are led to the conclusion that there are numerous other con- ditions affecting the amount of light wliicli a m THE HEAYENS. 143 planet obtains besides merely its mean distance from the sun. The Jovian satellites are subject to great variations in brightness, and in thek apparent size. The third satellite is that which is almost always the brightest; but from observations made in the year 1707, this satellite was found to have so much decreased in brilliancy, that its light was less prominent than that of the three other moons. It has been supposed that there are spots upon the satellites, and that these spots vary in extent; hence the brightness of the different moons would vary inversely as the size of the spots. There appears to be but little doubt that the satellites of Jupiter are surrounded by an atmo- sphere. M. Cassini in 1678 remarked that he could not perceive the shadow of the first satellite as it passed across the surface of Jupiter, although the spots upon it were clearly visible. Hence he concluded that the satellite was surrounded by an atmosphere which pos- sessed considerable refractive power, which thus 144 COMMON SIGHTS caused the sun's rays to bend round, and to decrease, if not entirely to do away with, the satellite's shadow. If this supposition be cor- rect, and these satellites do possess an inde- pendent atmosphere, it would appear that they are in a more advanced condition than our moon; and thus the planet Jupiter, with its attendants, may be a young solar system, the secondary members of which are passing through their great geological periods, obedient to a prearranged law, which shall fit them to support their various phases of vegetable and animal life, and at last to receive upon their surface the ima2:e of the Creator. The colour of the satellites is found to differ, although they shine merely by reflected light. Sir W. Herschel states that he found that the first satellite had a whitish tinge ; that the second possessed a bluish white, which varied slightly. The third was always white, whilst the fourth was of an orange-red colour. Later observers consider that the fourth satellite is of a bluish, and the thu^d of a yellowish colour, whilst IX THE HEATEyS. 145 that of the first and second inclines towards blue. A somewhat unphilosophical system has of late years crept into that which may be called exact science : this is, to assume that all the ancient recorded observations which do not ao-ree with the modern must have been incor- o rect. There is not the smallest reason to con- clude that there are no changes going on in the universe ; in fact, the whole history of the earth, geological and astronomical, gives direct evi- dence to the contrary. Geology especially teaches us that our planet has passed through a succession of long epochs, each of wliich dif- fered in conditions from its predecessor ; and thus that change is one of the laws which has been ordained by the great Architect of space, and of the worlds rolling grandly therein. \'\Tien it is asserted that ancient observatioiis must have been incorrect heccaise they differ from those of the moderns, we must premise that no changes have occurred, or are occur- rino', in those bodies which have been ex- 146 COMMON SIGHTS amined : and how can we know this ? We can merely guess that there is no change ; but our guess may be wrong. If, however, we reject recorded facts simply because they disagree with that which we at present see around us, we are putting aside those sound principles of investigation and deduction, which have led to some of the most important discoveries of modern times. The satellites of Jupiter may be under- going most important changes, which may cause their light to vary in colour and in- tensity. In the days of Sir W. Herschel they reflected light of one colour, now they may reflect another coloured light. It is these small changes, extending over long periods, which will probably, if fairly examined, enable us with our advancing collateral knowledge to grasp the key which will unlock some of those problems that have hitherto defied solution. But to deny facts simply because they may differ from that which we now see, is a proceeding which, if generally adopted, would enable us to IN THE HEAVENS. 147 demonstrate that EDgland had never been without railways or steamers, because we had always seen her furnished with both. If the disappearances and reappearances of Jupiter's satellites be observed, it will be found that at certain periods the sateUites will pass from the western side to behind Jupiter, and will, until they seem to touch him, continue bright. Instead of reappearing upon his eastern side, and being seen bright and distinct as before they disappeared, they will not become visible until they are at some distance from him. Then at another period the satellites would move up towards Jupiter as before; but they would not m their approach continue bright, but would disappear before they reached him. When they thus disappeared, they would reappear on the eastern side quite bright. These changes are due to the position of the shadow of Jupiter and the place of the earth, and they may be easily understood by an examination of the following diagram : — Suppose S the position of the sun, E F G the 148 COMMON SIGHTS earth's orbit, J K L the orbit of Jupiter ; the small circles round Jupiter are the course of his satellites. If the earth were at E and Jupiter at J, Jupiter's shadow would be thi'own in the dh-ection J H. As the satelKte moved around him, in the direction shown by the arrow, and reached the point A, it would then be lost sight of from the earth at E, because it would have moved behind Jupiter; the sun, IX THE EEATEXS. 149 ho^veve^, would have shone upon it as it dis- appeared, and tlierefore it would have been bright as it passed behind Jupiter. This same satellite would not reappear until it had cleared Jupiter's shadow, and had arrived at B : thus it would first become visible at some little distance from Jupiter, and upon the left-hand side. We find Jupiter at K (fig. 2), and the shadow thrown in the direction K X. The satellite moving around Jupiter as before would now disappear when it entered his shadow at C. This satellite would be at a considerable dis- tance from Jupiter when it was thus lost sight of, as will be evident by noticing how far the line E C is from Jupiter, for this line represents the line of sight from the earth to the satellite. This same satellite would be again seen froiD the earth when it reached the point D ; it would have been shone upon by the sun before it became visible, and therefore it would be seen to emerge from Jupiter quite bright. Thus in the second instance the satellite dis- appears before it reaches Jupiter, and reappears 150 COMMON SIGHTS close to liim. In the first instance it disappears close to him, and reappears at some distance from him. In consequence of the satellites having in some instances to pass behind Jupiter, and to move also through his shadow, they will be invisible during a longer period than when Jupiter and his shadow appear as one when seen from the earth. When -the shadow is behind Jupiter, the sun, earth, and Jupiter must be in a straight line, and at this period Jupiter passes to the south of all terrestrial localities at midnight. At this period his nearest satellite is invisible for about two hours and fourteen minutes ; but when the same satellite is observed, and Jupiter and his shadow do not appear as one, then this same satellite wiU be invisible for about three hours and a half. The eclipses of the satellites of Jupiter have served to reveal a very interesting law of nature — viz., that light requires a certain time to travel over space, or through that subtle IN THE HEAYEXS. 151 medium which exists between the yarioas worlds in the uniyerse. That there was a hio-h probability that the yelocity of light was not infinite was suggested as early as the time of Francis Bacon. It was not, however, until a much more recent period that the matter was definitely settled, although it is like most other problems — yery clear and simple when we knovj it. To show how it is known that light occupies some time to trayerse space, we will take a simple illustration : — Suppose E the earth, and X the position of Jupiter and his satelhtes, and let us suppose that B is another planet with satellites close to 152 COMMON SIGHTS Jupiter, and at exactly the same distance from the earth. Now let the nearest satellite of these two planets revolve at exactly the same rate, let the eclipses and occultations occur at exactly the same instant, and in fact let the two bodies A and B be exact counterparts of each other. AVhen the satellite was eclipsed at A, at that same instant would the satellite be eclipsed at B, the two phenomena occurring at the same time. Now let us suppose that the planet B and its satellite moved slowly away from the earth, and in the direction of D, the actual rate of the satellite's movements and the period of its eclipses being the same as before. If we now found that the eclipses of the two satellites at A and D appeared to occm^ simul- taneously, it would show that the velocity of light was infinite ; if, however, we saw that the satellite at A appeared to be eclipsed before that at D, it would indicate that light occupied some time to pass from D to A. If we knew IN THE HEAVENS. 153 the distance A D, and the difference of time between the eclipse at A and at D, we at once know the velocity of light. For instance, if A D were one million miles, and the difference in time of the eclipses one minute, then one million miles per minute would be the rate of light. The true velocity is much greater than this, being nearly twelve million miles a minute. As an additional example to illustrate the fact of the velocity of light, let us suppose that when the two satellites were eclipsed at A and B, a gun w^as fired from each planet A and B, the report of these guns would reach E at the same instant. Then the same event occurring we should find that as B moved away from E towards D the report of the gun fired from D would arrive after the report of the gun fired from A, and thus the velocity of sound could be ascertained. Let us substitute a ray of light for the wave of sound, and we have exactly the same result. The distance of Jupiter from the earth varies 154 COMMON SIGHTS considerably ; lie is nearest when he passes the south at midnight, and is farthest when near the sun in the heavens ; and thus, by the variation in his distance from the earth and the number of his eclipses in a given time, a means is found to indicate the velocitv of lio-ht. PL6. MARS. "^Sncent Brooks.IiLK. Spots on Mars and white patches at the poles, p rob ahly snow. IN THE HEAVENS. 155 CHAPTER VII. MARS. A LARGE briglit-red looking object in the sky, which does not scintillate like a star, and which is visible in a portion of the heavens different from that in which the sun has set, is most likely to be Mars. In consecjuence of this planet lying farther from the sun than the earth, it is visible in all parts of the heavens, and is thus unlike Venus in its motion. He will appear larger and brighter when due south at midnight than at any other time^ because then he is much nearer to the earth. Mars approaches the earth more closely than any other planet except Venus, as he is dis- tant about fifty million miles when he is nearest to us : thus an express train, travelling at an imiform rate of fifty miles an hour, would 156 COMMON SIGHTS pass over the shortest distance which separates Mars from the earth in about one hundred and twenty years. Mars is a very small planet, his diameter being rather less than four thousand miles, although from his proximity to us he is often a very remarkable object in the heavens. Placed beside the earth the relative dimensions would appear as below : — ( mars] EARTH \ We have mentioned that Venus always ex- hibits phases, like the moon, and is never visible when fully illuminated, whilst Jupiter invariably appears round and bright. Mars, however, can at times be seen when the whole surface is not visibly lighted by the sun, and then his appearance is like that of the moon when within a few days of the "full." The phases of Mars are visible to us, because we IX THE HEATEXS. 157 obtain a side view of tlie planet wlien he is nearly in the same part of the heavens as is the sun ; whereas, owing to the distance of Jupiter, we cannot see any part of his surface that is not illuminated. As early as the year 1610, Galileo perceived that 3Iars was not at times perfectly round. The year of 31ars, being one terrestrial year ten months and two days in length, is nearly as long as our own. When a telescope of moderate power is directed towards 31ars, several spots are ob- served upon his surface : many of these are per- manent, and Cjuite distinct. They appear in groups and of various shapes, the gTeater quan- tity being situated in northern regions. UjDon the same principle that we were able to tell that Jupiter rotated upon an axis, we also know that Mars partakes of this almost univer- sal movement. Thus the day and night alter- nate upon this planet, the period from the noon of one day to that of the next being about twenty-four hours and thirty-seven minutes. 158 COMMON SIGHTS Thus his day and night do not vary much from the length of our own. The spots upon his surface also show that the annual alternations of climate are not very different from those on earth ; the variation in altitude between the midsummer and mid- winter sun being about fifty-seven degrees, whilst on our world it is forty-seven degrees. There is not, therefore, the great alternation of cold and heat which occurs upon Yenus, nor the uniformity of climate which exists upon the surface of Jupiter. Amongst the various in- teresting facts which the telescope has re- vealed, not the least is that of the rotation of the planets in our system upon their various axes, in such a manner that they all have either a slight or great variation of season, and thus that summer and winter alternate upon the surface of each world. That there is every reason to conclude that change of season is experienced on Mars may be shown by the circumstance that around his poles during their winter season appear brilKant white IN THE HEAVENS. 159 spots, Tvhich have fairly been looked upon as accumulations of snow. The spot around the north pole increases in size as the northern winter approaches, and is largest at mid- ^yinter. When the spring and summer ap- proach, the white gradually diminishes, until at midsummer it is scarcely visible around the north pole. Thus, when each hemisphere is in winter, the white spots around the pole become apparent ; then when the summer approaches, the spot disappears. These white spots appear more than double as brilliant as any other portion of the surface of Mars ; and as they merely extend to about the same distance from the poles of Mars that our arctic and antarctic snows reach fi'om om^ poles, it is reasonable to conclude that the climate of this red planet is not very different from that of our own. It has been found that during the winter of Mars the snow extends to about thirty-five degrees from that pole which is in winter, but in the summer the snow is not more than six or seven degrees from the same pole. This is really 160 COMMON SIGHTS that which we should expect from the alterna- tion in altitude of the sun between winter and summer ; for in summer he would rise at mid- day about five degrees higher than our sun rises to us, and in midwinter he would be at a less altitude at midday than our sun, by the same quantity. Thus the arctic circle would in Mars extend to about tw^enty-eight degrees and a half, whilst our arctic circle reaches only to twenty-three degrees and a half from the poles. It is indeed a singular fact that we can thus gaze upon another world, can observe the changes of climate upon his sm-face, and we may thus keep a register of his severe and mild winters. To even have hinted at such unheard-of wonders a thousand years ago would have aroused the ridicule of many an em23ty- headed critic, as would also the idea of much which we now have realized. Who shall ven- ture to declare that in future ages a means of communication may not be discovered between other worlds and our own, perhaps by the aid IN THE HEAVENS. 161 of forces as far beyond the subtlety of our present electrical force, as the delicacy of this communicating agent is beyond that of the few methods of telegraphing, or signalling, known to the philosophers of the early ages ! It was once supposed impossible to make a signal beyond the limits of material terrestrial vision ; now, however, it is supposed that where we can establish the material conductor there only can we telegraph, for it is necessary to lay the wire by which to speak. Who knows, however, what the future may reveal, and how much yet re- mains for unborn generations to glean ! M 162 COMMON SIGHTS CHAPTEE VIII. SATURN. We have now to describe a world which pre- sents peculiarities not in accordance with those which characterize any other member of the solar system, with which we are acquainted. Although not a very brilliant object in the heavens when examined with the unaided eye, still when the telescope is used, Saturn becomes a most interesting sight. Nearly spherical in form, like the other planets and worlds, Saturn is furnished with an appendage, the purpose of which is not known. Extending around him there is a sort of brilliant hoop, which does not touch him in any part, but yet seems to be a material substance. In addition to this hoop, or " ring " as it is termed, there are at least eight moons attendant upon Saturn. His size JUPITEPu and liis Satellites . PI. 7. SATUR^^ and Ms E in^ . "feiceiit Brooks.litJi IN THE HEAVENS. 163 also is considerable, he being nearly seventy- six thousand miles in diameter : thus from his size, attendant ring, and numerous moons, he becomes a most important member of the solar system. Saturn, like Jupiter and Mars, may be seen in all parts of the heavens, for the planet is much farther from the sim than the earth is, which consequently may be between the two former bodies : thus Saturn may pass the south at midnight. In consequence of Saturn appearing some- what like a star, although he does not twinkle, it may aid the amateur to find him in the heavens, if we give a diagram, showing where Saturn is to be found during the next thirty years. No other knowledge will be required to enable the reader to comprehend the sketch, than to remember that the earth turns round during twenty-four hours, and that at noon the sun will be south. In the centre of the accompanying diagram is the sun ; four small spots round this show four positions of the earth during the year. 164 COMMON SIGHTS These four positions are marked December, March, June, and September. At twelve How Saturn may be found until a.d. 1882. Ncfv^l861 1870 Saturn's Positions. o'clock (noon) the sun is due south ; therefore, in December, at midnight, the south would be in the direction opposite to the sun ; con- sequently A would be south at midnight. In December, 1861, we should find Saturn nearly south-east at midnight, because A being south, Saturn is seen on the left. IX THE HEATEXS. 165 In March, 1863, Saturn would be south about midnight; in June, 1870, also south at mid- night. As all the celestial bodies move from the east towards the south, we have merely to remember that they pass from east to south in six hours, consequently fr^om south-east to south in three hom's. Thus if a body is known to pass the south at midnight, it will be found in the south-east at nine p.m., the south-west at three a.m. Then suppose we wish to know where to find Saturn at nine P.3i. in 3Iarch, 1862. Xine p.3I. would be half way between six P.M. and midnight, and therefore our south would point in that direction at that hour. "We see on the sketch where Saturn would be in 1862. Thus, at nine p.m. in 3Iarch, 1862, he would be a little to the left of south. An examination of this diagram will show where to find Saturn at all times of nio-ht and of the year, for the next thiity years. Saturn is much farther from the sun than either Jupiter or Mars, and as a consequence 166 COMMON SIGHTS his year is a long one, consisting of twenty- nine of our years, five months, and sixteen days. A terrestrial mortal, therefore, if a resident upon Saturn, and yet subject to terrestrial con- ditions, would barely live long enough to see three summers ; for if he died at the mature age of eighty earthly years, he would still merely be three years old, according to the years of Saturn. In s|)ite of the large size of this singular planet, still he rotates with gTcat rapidity, his day and night consisting of only ten hours and twenty-four minutes. Thus a terrestrial day and night are longer than two of Saturn's ; and therefore during a given period the sun rises and sets to the Saturnites more than twice as often as he does to the earth-dwellers. The ring of Saturn also spins round, and with a velocity almost equal to that of the planet, as it rotates in about ten hours and forty minutes. We have before mentioned that all the planets and satellites shine only in conse- IN THE HEAVENS. 167 quence of being lighted by the sun ; it is found, also, that this ring of Saturn is visible only from the same cause ; for the shadow of the ring is distinctly visible upon the body of the planet, whereas if the former gave out light there would be scarcely any shadow. Also it is found that the planet casts a shadow on the ring, and thus it is known that the former shines at least mainly by reflected light. We have spoken of tJie ring of Satm^n, but the . appendage referred to really consists of several concentric rings, which appear to be separated one from the other. The extreme diameter of the exterior ring is about one hun- dred and seventy-six thousand miles, and it extends to upwards of forty-eight thousand miles beyond the surface of the planet. The breadth of this exterior ring is about ten thou- sand five hundred mUes, whilst its thickness is not more than two hundred and fifty miles. From this earth the ring of Saturn will not always appear of the same shape, because, owing to the movement of the planet around 168 COMMON SIGHTS the sun, and with an axis inclined from the per- pendicular, we sometimes see the ring of an elliptical form, or as a straight line. In the dia- gram which we have given to show the position of Saturn during the next thirty years, we have also shown the relative position of the ring as it would appear from our earth. It will there be seen that in the year 1861 the ring will appear like a thin streak of light; whilst in the year 1868 it will be in its most open form, and therefore best suited for observation. Conjectures have of course been made as to the formation of the ring of Saturn. One of the earher astronomers of modern times * sup- posed that a number of satellites were strung together, and thus formed a continuous body. Another individual believed that Saturn was once much larger than he is now, and that the ring is a sort of remnant of the planet, and which has not shrivelled up like the remainder. Then it has been supposed that a comet was captured by the gravitating influence of Saturn, and the * James Cassini. IX THE HEATEXS. 169 comet's tail has now attached itself to the equatorial regions of the planet. In ahnost all the conjectures which have been made in con- nection with this body, there is one preliminaiy proposition which appears to have been assumed — viz., that the ring was not always an ap- pendage of Satm^n. We now know that the ring is not a number of satellites strung toge- ther, and we also perceive that it is far more solid than the tail of a comet ; and thus two at least of the speculations are worthless, whilst the other mentioned is untenable fi^om an absence of facts upon which to base it. Within the last few years it has been shown that several changes are occmTing in Satiu'n's rings, a new ring having been foimd to separate itself from the others. This is a fact tolerably well ascertained ; and it is an interesting one, inasmuch as it indicates that changes of some kind are occmTino- in at least one of the mem- bers of this system. WTien the siuiace of Saturn is examined with high magnitH'ing power, several streaks or 170 COMMON SIGHTS belts are observed, somewliat similar to those visible upon Jupiter: these belts do not run across the planet parallel to the rings, but they incline to and from them to the amount of several degrees. The polar regions of the planet are found to vary considerably in brightness — a fact which seems to indicate the presence of an atmo- sphere, or of changes of temperature. Saturn is attended by at least eight moons, or satellites, which revolve around liim at dif- ferent distances. The nearest moon to him is little more than half the distance from his surface that our moon is from us, and it moves around him in a period of about twenty-two hours thirty-seven minutes. Owing to the dis- tance of this body, and the position of his ring, the eclipses of the satellites cannot be observed with such facility as those of Jupiter's moons ; but to be able to perceive the eight moons of Saturn is a proof that the telescope with which we observe is a good one. IN THE HEAYEXS. 171 CHAPTEE IX. UEAXUS AXD XEPTUXE. Beyoxd the orbit of Saturn, and at a vast dis- tance from tlie sun, there are two worlds which far exceed in size our own earth. One of these, Uranus, moves round the sun in about eighty-foui' of om^ years, and is distant upwards of eighteen hmidred million miles from the sun. The other, Xeptune, occupies nearly a hundi'ed and sixty-five years to move round the sun, from which he is distant about two thousand eight hundred and seventy million miles. From the great distance of these two planets they present very few peculiarities to the eye of the common observer ; for unless examined with telescopes with very high magnifying powers, their diameters even will not become appreciable. Both these planets are attended with satellites, probably with many; eight, however, are usually assigned to Uranus, and 172 COMMON SIGHTS one or two to Neptune. We have mentioned that it appears to be a rule that the satellites attendant upon a planet invariably move round their primary in the same direction that the primary itself rotates. Thus the satellites of the earth, Jupiter, and Saturn move around from west to east — that is, from right to left if they Avere seen from the northern regions, but from left to right if seen from the southern. If we observe the satellites of Jupiter from the northern hemisphere, we shall find that when they are moving from right to left they will pass behind the planet, but when moving from left to right they will pass across his disc. Thus if N S i^ were the north and south poles A. (^ C of Jupiter, a satellite would ^ revolve round him from A to B, when it would appear upon Jupiter's disc ; it would then move on to C. Thus it would move from west to east round Jupiter. If now we were to turn the axis N S down into a horizontal position, and still keep the satellite revolving round the equator of Jupiter, IN THE HEAVENS. 173 we should see the satellite move thus — from A to B, C, and D (upper figure), or from our west over to our east, or thus — / A- / from A to B, C, and D (lower figure) ; that is, from our east over to west, just as we turned the north or south pole towards us — hence these moons would move with left or right hand rotation, just as the north or south pole of Jupiter w^as tm-ned towards us. The satellites of Uranus appear in this manner, in consequence of the axis of the planet being turned down, as it were, hori- zontally, so that during forty-two years they 174 COMMON SIGHTS would appear to move from east to west, or retrograde, as it is termed ; then for forty-two years they would appear to move from west to east, or direct. Some slight confusion has been allowed to exist in connection with the movements of these bodies, some Aviiters having gone so far as to state that their motion was at variance with that of all other satellites. The fact is, however, as shown above, a simple change in their apparent movements, according as the one or the other pole of Uranus is directed towards the earth ; and as the same pole remains turned towards the earth for forty-two years, the fact of a change occurring was overlooked. We should not be warranted in asserting that the sun moved in opposition to the rules of the solar system when we observed him from the southern hemisphere, and when consequently he moves from right to left each day ; neither ought we to state that the moons of Uranus move in an irregular manner, simply because sometimes they will be seen to move with right- IX THE HEAYEXS. 175 hand rotation, and after many years with left- hand, just as the north or south pole is tui^ned to- wards the sun and earth. It cannot even be said that the position of the axis of Uranus is an un- usual one, for we know not what is the most general position, no two planets being exactly alike. The inhabitants of Uranus might as well state that our earth's axis was in an excentric position, because the sun was neyer vertical at midday bevond twentv-three and a half desTees on each side of the equator, whereas to them he was sometimes vertical, even in polar regions. In fact, it is not philosophical to take our own tiny earth as a model of perfection, and to assume all other worlds either imperfect or in an excentric condition, simply because they are sKghtly different in some details. Each, pro- bably, is admh-ably suited to its position and constitution, and may be where it now is, simply because, by a prearranged law, it has reached the locality to which its atoms at pre- sent bear an affinity, and where it will maintain the balance of the universe. 176 COMMON SIGHTS The diagrams below will show the relative positions of Uranus and Neptune during the next forty years, the rules for finding them being the same as those for finding Saturn and Jupiter. The ring next the earth is the orbit How Uranus and Neptune may be found until a.d. 1900. of Uranus, the exterior that of Neptune. Thus, referring to Uranus, we know that during May, June, and July, from 1861 to about 1876, he would not be visible because behind the sun. IX THE HEAYEXS. 177 During Xovember, December, and January, however, of the same years he will pass the south at about midnight. About ]\rarch; from 1883 to 18S6, Uranus will be found to the south at midnight, whilst at the commencement of June, 1900, he will be south about mid- night, and not visible in December or Xovem- ber. Xeptune will not be visible in February, 3Iarch, or April, for the next ten or fifteen years ; September and October being the two best months for examining this remote planet for the next twenty years. Mercuey. At certain intervals of about one hundred and twenty days a small brilliant red-coloured body -v^ill be observed in close proximity to the sun. The body to wliich we refer is the planet Mer- cury, which is situated at a mean distance of about thirty-six million miles from the sun. Mercury, like Yenus, will be seen sometimes as a mornino; and at other times as an evenino; star, N 178 COMMON SIGHTS but it will never appear so far away from the sun as will Venus. Tlius either immediately after sunrise, or oefore sunset, this planet must be looked for. This little planet, which it is supposed measures less than three thousand miles in diameter, rushes round the sun in a period of about eighty-eight days. Thus the year of Mercury is only about one-fourth the length of our own, and if we lived to be sixty years old on our earth, we should be about two hundred and sixty years of age, counting by the years of Mercury. It is found that, like all the other planets in the system. Mercury rotates upon an axis, and occupies about twenty-four hours and five minutes in rotating. It is assumed that Mer- cury rotates in such a manner that the sun will be vertical each year at midday at all localities, except those within twenty degrees of the polar regions. Thus, in consequence of the quick return of the seasons, and the ex- tension of the tropical regions, there would be but little time for ice to form upon any part of IX THE HEAVENS. 179 Mercury, as the sun would be absent merely a few days even from the extreme northern re- gions; thus a very uniform climate ought to prevail in that planet, which, with the quick return of the seasons, would probably be very suitable to the rapid growth of vegetation, espe- cially so of that type of vegetable found so abundantly in our coal-fields. If then ilercury possess a soil and an atmosphere at all analo- gous to those of our earth, we might suppose that the little planet was now engaged in coaling. It has been supposed by some observers that there are very enormous mountains upon the surface of Mercury of a height sufficient to alter the shape of the crescent which this j^l^^et sometimes shows. Like many other delicate observations connected with science, some ob- servers assert, whilst others as vigorously deny, that these excrescences exist. Mercury is seen occasionally to pass across the disc of the sun, when it appears a romid opaque body, attended by a sort of atmosphere. 180 COMMON SIGHTS The passage of a planet across the sun is called " a transit " across the sun's disc. During the next forty years six transits will occur ; viz. in— 1868 . . . Nov. 4. 1878 1881 1891 1894 1901 May 6. Nov. 7. May 9. Nov. 10. Nov. 4. The planet will occupy about from four to six hours in passing across the sun's disc, and therefore can easily be distinguished from a spot in consequence of the rapidity of its motion — a spot appearing to scarcely change its position during a whole day. CONSTELLATIOKS. d ai e f ?] 8 fe/ IiQ.2. a^a . Betelgeux . e .e . ilitf el i^t^. 2. l3."b Oi-ioTislDelt. f -f . Tjeflatrdx . Cassiopeia. Q. c. Siciiis . Gr.G. ^Mdebaran . Tig. 3 . d. d . Saipli . li."h n ei ajd.e3 ^^orth ern Cro^vn . ai . The Pointers . '/mcerd 2rooT<s hxh leg. 4. l.l.Tega or alYTse . 1.2. The Pole Star. 13. CapeHa 4.4 . The Great Bear. IN THE HEAYENS, 181 CHAPTEE X. THE FIXED STAES, To tlie mere casual observer the stars appear to be scattered promiscuously in the heavens, and to have no special characteristics which can distinguish them from each other. A very little attention will, however, show that they differ in apparent size and brilliancy, that their colours vary, and that they are formed into groups or patterns which can, when once known, bo easily recognized. We have mentioned that some of the so-called stars are really planets similar to our earth, which would probably look like a small star if seen from one of them. These planets wander amongst the fixed stars, but around a particular course : and are therefore to be found at various periods near to various gToups of stars. The fixed 182 COMMON SIGHTS stars, as the name implies, never move, or if they do, it is merely by the aid of delicate instruments and long examination that these movements become manifest Hence a group of stars can always be recognized because the various members do not alter their relative positions. If the stars be attentively observed for a year, it will be found that during summer very different constellations will be seen in various parts of the heavens to those which are visible in the same localities in winter. Some bril- liant constellations, also, which we may observe dmdng one season are invisible during another ; other constellations likewise are always to be seen, but are found in different parts of the sky, according to the time of the year. From the very earliest ages names have been given to the principal stars, and also to the constellations which are the most prominent in the heavens. Thus individuals are enabled to speak intelligibly in connection with the sky, just as we can with reference to various parts IN THE HEAVENS. 183 of the earth ; for if there were no such names as Africa, xlmerica, &c., the world would to us be a confused and indefinite accumulation of land and water, just as would the heavens if the stars could not be known by name. If an individual acquainted with the names and positions of the yarious stars were to tell another Avho was ignorant of them that a comet or a meteor had been seen moving from Sirius towards Capella, the information would be about as interesting and instructive as though we told a Bushman that there was free trade with France. So far beyond the range of his knowledge would such an intimation be, that he would probably not trouble his mind about the matter. When, however, we know the direction or position thus pointed out, and also picture to ourselves the probable course of the comet, resulting from its movement in the direction indicated, and compare this course with that of others of which we have read, we begin to take an interest in the subject, simply because we understand something about 184 COMMON SIGHTS it. For it really appears as though individuals were not only indifferent to, but even often disliked some subject, simply because they were unacquainted even with its mere outline. We will first endeavour to explain why it is that there are some stars which can always be seen in these latitudes ; after which some of the principal constellatioi^s will be shown, and also their positions at various periods during the year. A moment's reflection wdll show^ us that our view is bounded by the horizon; we cannot, therefore, see that w^hich is below the horizon ; all, however, that is above may be seen. Then let us remember that our earth turns round during about twenty-four hours, and we can understand the following sketch. Suppose the position of any person upon the earth, say, for example, in England, then the line HOE would represent the horizon of this person, and all that w^as above this horizon might be seen ; therefore various bodies that were situated as T E S A P and X, would IN THE HEAVENS. 185 all be visible from 0. P would be nearly over- head, A near the horizon, and lo\Yer down than T. P TRSA -^^ X •■•Jiiii/ In twelve hours' time, the same person would be carried by the rotation of the earth round to Q, when his horizon would be represented by the line P Q IT, From the position Q^ E would seem high above the horizon, and A much higher than T. P, which was nearly overhead when the person was at O, would now be just on the horizon, and X which was seen from 0, vfould be invisible from Q. Thus T E S A ^vould be seen from both and Q. The principal difference being, that at 0, T was above A, but from Q, A was above T. This chano-e would arise merelv from the 186 COMMON SIGHTS fact, that the head of the observer pointed to a different direction at from that in which it pointed at Q. If T E S A are called stars, they would also be always visible from the positions and Q, bnt X would be a star only visible from 0. The stars can only be seen during the night ; and in consequence of the earth moving around the sun, night Vvould occur on the side or Q according to the time of year. \Mien the night occmTed on the side 0, then the stars T K S A and X would be seen, T being above A. When the night happened on the side Q, X would not be visible, but T E S A would be seen, A being above T. Hence there are some stars which are always visible during the night from certain localities, these stars beins: sometimes nearlv overhead or close to the horizon, according to their position in the heavens and the time of year. Amono' the stars which can alwavs be seen from England, the following are the principal. The constellation of the Great Bear, also the IX THE HEAYEXS. 187 Pole-st^ir and the Little Bear. The constellatiou Cassiopeia, the bright star Capella, called also Alpha Aiirigae, the bright star Alpha Lvr^. called also Tega. can just be seen on the horizon from the south of England when it is lowest, and to the north of us. At other times it will be found high up, and to the south. Alpha Cygni is another bright star always visible from England. To enable any person to find the position of the various principal stars at any time of the year, the following sketch is given : the method to be adopted is similar to that for finding Saturn, Uranus, &c. Thus we have merely to re- member that the sun is to out' south at midday, to our north at midnight, and that the earth turns round in about twenty-foui^ hours. Allien the sun is between the earth and a star, the latter is of course invisible, owing to the sun- light. By remembering these simple facts, the following sketch becomes intelligible. The sun is shown in the centre of the dia- gram, the earth in four positions according to the time of vear. 188 COMMON SIGHTS For illustration let us see which stars are to our south at midnight in December. Capella. ^ Cassiopeia. o. Andromeda. Alpha CygnL At noon, the sun is to oui^ south, consequently twelve hours after noon, that is, at midnight, our south will be in the opposite direction. Thus Orion^ Eigel, Betelgeux, &c. would be in the southern heavens at midnight in December. At about 9 P.M. at the same season, a Persei and Aldebaran would be nearly south. Stars in the direction of Ve2:a could not be seen IN THE HEAYEXS. 189 because of the sun, unless tliey were near tlie northern pole of the heavens. In Septemljer Alpha Cygni would be south about 9 p. M,, Cassiopeia and Andromeda about midnight. In June, we should not be able to see Sirius or Orion in consequence of the sun, whilst Capella would be in the north, and visible, because it is one of those stars always seen from England. Vega would be south at midnight at this period, and Altair at about one o'clock in the morning. Thus, by remembering in which direction the earth tmms round, we can always find by this diagram the position of the principal groups of stars. In March, at noon the sun is south ; at 6 p.3i. Orion, Sirius, and the stars near them ; at 9 p.:m. EegTdus ; at about midnight Spica ; at about 3 A.:\r. Arcturus and the Xorthern crown; about 6 a.:j:. Yega and Altair. Ako at mid- night Sirius will be in the west, and setting, Yega in the east, and rising, A sketch of some of the principal groups of stars is shown in 190 COMMON SIGHTS Plate 8, so that they may be recognized by their forms. In addition to the diagram which we have given, the position of the various stars may be ascertained by the aid of the constellation of the Great Bear and one or two other stars. The Great Bear is snch a remarkable constel- lation that it can easily be found at any time ; and hence the Pole-star can be found by the aid of the pointers. Then if a line be drawn from the Pole-star at right angles to a line from the pointers to the Pole-star, then this line will pass close to a bright star called Capella. A line from Capella through the Pole-star will, if produced, pass through a bright star called Vega or Alpha Lyrse ; thus Capella, Vega, and the Pole-star are in nearly the same straight line. If a line be drawn from the Pole-star through the last star in the Great Bear, this line pro- duced will pass through Arcturus, a bright reddish star, famous to all observers as the star IN THE HEAVENS. 191 near which the brilliant comet of 1858 was seen when in its splendour. The belt of Orion is another constellation easily recognized, hence Sirius becomes known (see Plate 8), also Betelgeux and Eigel. Then on the opposite side of the belt to that on which Sirius is found, and nearly in the same straight line, we find a star named Aldebaran. Smus, Betelgeux, and a bright star named ProcYon, will form an almost equilateral triangle. At about one-thuxl of the distance from Arc- turus to Vega we find a semicircular group of small stars, one of the gTOup being large. This large star is named Alphacca, the group being the Northern Crowm. About midway between the Pole-star and the tail-star of the Great Bear, and nearly in the direction of a line joining these two, is the brightest star of the Little Bear. A few minutes' attention directed to the heavens any evening will soon enable an individual to know some of the principal stars, and to find them, if visible, at any time of tlie 192 COMMON SIGHTS year. The principal groups of stars, such as the Great Bear, Orion, Capella, Cassiopeia, or the Northern Crown can be recognized by theu^ form, some of the large solitary stars by theu^ position relatively with the Great Bear and the Pole-star. There is a vast field for speculation and ad- miration in the illuminated page spread before us during each clear night in the year. When we realize the fact that each twinkling star is a sun, the centre probably of a system of re- volving worlds, each of which may be similar to that on which we dwell, we become bewil- dered amidst so much grandeur, and may well stand insjDired with veneration and awe if we reflect upon our own insignificance com- pared with the extent of creation. "Wlien we behold these millions of suns glittering in the midnight heavens, v/e natm^ally ask, for what are they intended? It has been said that* they are to give light on earth, and this is their most obvious use; but is it their only purpose? Have all these gigantic bodies, each of which is IX THE HEAVENS. 193 ten tliousancl times the size of our pigmy world been created solely for the purpose of casting at rare intervals a dim Kght upon us. Such a conclusion would partake somewhat of the self- sufficiency of man, but would scarcely show that we realized the perfect system which has been adopted in creation, and the endless variety and originality which observation teaches us really exists. As far as we can judge from facts, it is sup- posed that the sun is a solitary member of om* system, and that although attended by many planets or satellites, he is still without a com- panion. We cannot, however, say whether if our sun were seen from the Pole-star he would ap- pear alone» It is probable that he would ; and thus he presents a variation from other stars in the universe, some of which possess companions, which give out light and revolve round each other. Thus two suns belonging to one system would appear to indicate a higher or more advanced state, and at least to remind us that in creation there is an endless variety, both as o 194 COMMON SIGHTS regards suns, systems, and worlds, or the most minute insects that creep around us. Like most novelties, the early announce- ment of the fact that several of the stars were double, excited ignorant or bigoted critics, who compared this supposed condition of the stars to the pairs of soles on a fishmonger's stall. Now the most accurate observations have shown that these stars move round each other, and thus from year to year they alter their relative position ; hence the name of fixed star is a mis- nomer. The tliird star from the tail of the Great Bear is a double star ; the two stars appearing to move round, or the one to revolve round the other, in a period of about fifty-eight years. Castor, one of the twins, consists of two stars ; a period of about two hundred and fifty years being assigned to the revolution of one of these. Eigel, the Pole-star, e Bootis, y Virginis, a Hercules, and many other remarkable stars, are double ; in fact, nearly six thousand double stars are alreadv known. DOTIBLE STARS (Telescopic) Ti.d. 1 /3 CjoTd .3a Geminoruin . b/x Saoittaiii 2 S Bootis . 4 '■n Cassiopeia. 6 Polai^is . 7. 51 Iibrce. IN THE HEAVENS. 195 Arcturus is a star which the reader will now be able to find. About ten degrees to the north- east of Arcturus, or, more definitely speaking, about ten degrees up a line drawn from Arc- turus towards Vega, we find a star called Miraeh, which is double, the contrast of colour between the two stars being yery beautiful. In addition to double, there are some groups of triple and quadruple stars ; the star ap- pearing single when seen with the naked eye, but triple or quadruple when examined with a large telescope. By examining the records of ancient astro- nomers it has been found that there are varia- tions in the brightness of the stars ; some appear to be getting dim, whilst others are more brilliant than formerly. Some stars have dis- appeared entu^ely, as vv^as the case with the seventh star of the Pleiades, which it was said vanished when Troy was taken. In modern times it is found that several stars vary in brightness dming certain periods, some occu- pying from five to ten days to pass through 196 COMMON SIGHTS their changes, whilst others occupy three or four hundred days in returning to their same condition. In some instances a star of large size has appeared merely for a short time, and has then suddenly been lost sight of. The principal object to be observed in con- nection with the stars, if provided with a tele- scope, is the relative position of the double stars, and the beautiful diversity of colour existing between them. A^Tien the two stars become visible in the telescope, it can then be seen that they are usually of different colours. Some of these contrasts are very lovely : a rosy tinge is possessed by one star, its companion perhaps a beautiful green ; this is the case with a star called 24 Com^ Berenicis. The prevaiKng colour of the attendant stars is blue or greenish blue. Sometimes they are of the same colour as the principal star, but this is not usual. It is found that certain stars which formerly shone with a white or red light, now appear of a different colour, and thus there appears to be IN THE HEAVENS. 197 a change of some kind occuiTing in every portion of the universe. If we examine the earth beneath our feet, we find tha.t from the very earliest ages to the present time there has been one continued change, or onward movement. We may per- ceive cropping out in various localities an ac- cumulation of hard rocks which formed the surface soil in ages long since past : these rocks were not capable of affording nourishment to plants or trees until they had been submitted to certain actions during long periods of time. Again, we find that m a subsequent epoch plants of various kinds flourished abundantly, whilst the earth was still untenanted by a numerous class of the animal creation : then we recognize a period when animals of vast size roamed over our now fair earth, and reigned monarchs of the plain, forest, and river ; man being still an unknown creature in this planet. History teaches us that there was afterwards a time when vast hordes of men peopled the world, whose minds were comparatively con- 198 COMMON SIGHTS tract ed, and whose aims were limited. If a modern savant with his knowledge of tele- scopes, steam, electricity, photography, and other scientific facts, had existed some seven or eight hundred years ago, he would probably have been treated as a deity by those who were then capable of perceiving the utiKty of the subjects with which he was acquainted. Thus we find amongst men that progeess has been one of the most prominent characteristics. Hence from the period of hard unfertile rock to that of the present day, there has been one onward movement ; and even now we are livmg in an epoch which daily presents some change by which the crude or erroneous opinions of the past become trimmed so as to more nearly ap- proach truth, and hence to be more in harmony with that Divine wisdom which has created all the vast celestial machinery as well as the minds by which his works can be compre- hended. When we find that there are stars which disappeared, changed theu^ colour, ap- peared or are variable, we are induced to reflect IN THE HEAVENS. 199 upon the probable cause or purpose of these changes, and to form conjectures as to the various appearances which our own earth might have presented at different times. It is at least probable that vfhen a star changes its apparent colour there is some change of con- dition in that star. Perhaps its atmosphere may have become affected by the approach of some other celestial body; the electrical or magnetic condition of the star may have varied, or the body may be passing through various epochs and in rapid succession, much in the same manner that om^ own planet passed through changes which occupied ages of time before they were completed. To know that creation is not stereotyped in one form is a most interesting fact ; and we become aware of this whether we observe the distant suns and worlds, or examine the earth beneath our feet. 200 common sights Nebulae. An attentive examination of the sky during a clear night will enable an individual, even with the unaided eye, to perceive several whitish-looking foggy patches of light, which appear somewhat like the mist which at times surrounds a bright star. If a telescope of even the smallest power be turned towards these patches, it will be found that they consist merely of an accumulation of small stars grouped very closely together. When the telescope is dnected to various parts of the heavens, there will be seen many of these misty patches, which then appear with the aid of the telescope very similar to the groups of small stars if examined with the unaided eye. These groups or patches of misty matter are called Nebulse. With the aid of the most powerful telescopes some of the so-called Nebulae have been resolved as it is termed ; that is, they have been found to consist merely of groups of stars in close proximity to each other. There are still, :pi.iO. :NrEBrx^ . I. In Hercules. 3. In Cassiopeia. o.DumLBell m Mupeada. 2. ,, Aitinous. 4<. ,, Andromeda. 6. In Lyra. IX THE HEAYEXS. 201 however, several nebulae which no telescopes have resolved, and which appear misty even when examined with high magnifying powers. An observer who may be provided with any small telescope will find that he is able to resolve some of these patches of light. Alde- baran is a star easily found from the descrip- tion already given; close to Aldebaran there is a group of stars which to the unaided eye presents this misty light appearance. There are also two patches close to Cassiopeia. 202 COMMON SIGHTS CHAPTEK XI. COMETS. The most mysterious bodies in the heavens are certainly comets. The planets we can readily imagine to be, and there appears every probabi- lity that they are, the residence of created beings of some kind. The sun and the fixed stars ap- pear to be the centres of systems to which they contribute light and heat. When, however, we examine the form and condition of these sin- gular wandering bodies which are called comets, it is difficult to conceive that they are as yet fitted for the residence of any material beings ; and it would be no less in opposition with the analogy of nature, to assert that they have not their use in the economy of the universe. In ancient times, it was the custom to state and believe, that comets produced diseases and losses to princes, as well as to peasants, and they Pl.ll. COMETS 1 . Encke's . 2. Comet of 18 IX THE HEAVENS. 203 were thus considered messengers of evil. In more modern times these visitors were sup- posed to be the vehicles in which the spirits of the departed were conveyed to some special locality assumed to be that of Paradise. Some of the ancient philosophers behaved comets to be a sort of meteor which existed in the atmosphere of the earth ; whilst others ven- tured very daring and, for theu^ time^ unor- thodox opinions, and asserted that comets were probably nearly as high up as the moon. Comets may be divided into two classes, viz., those whose course is known and whose reap- pearance can therefore be foretold, and those whose course is unknown, and whose visits are therefore imcertain. There are some comets whose course is known, and whose return to any point in the heavens can be predicted ; but these are insig- nificant in appearance when compared to some of those brilliant visitors, which gleam for a period in the heavens, and then dash away into endless space. 204 C03I3ION SIGHTS Comets first become visible to us in a variety of ways. The mere searcher of the heavens, who night after night directs his telescope to various parts of the sky, may at length perceive a small speck of light which differs slightly in appearance from a star. An examination of this body dm^ing a few evenings, may show that its position changes very rapidly, and that it is moving amongst the various fixed stars. The first fact resulting from this discovery would be, that the speck of light was either a planet or a comet, and a very few evenings would enable an observer to decide which of these bodies he had discovered. If the comet were approaching the sun, it would probably become more and more distinct each night, and would soon become visible to the unaided eye. When thus distinct it usually appears like a small star, with a slight ray of light shooting out from the bright portion. The mere casual observer might not at first perceive any difference be- tween this comet and a star ; but a little atten- tion would soon shovv^ the difference between IX THE HEAYEXS. 205 the two. If the comet were a large one, and passed near the earth, it would become not only a remarkable, but a splendid object in the heavens. There can then be distinctly seen a bright head, or nucleus, as it is termed, and from this there are diverging rays of light or vapour which extend to a considerable distance behind the head of the comet. This brilliant body moves on with great rapidity, and is at length lost sight of in consequence of its approach to the sun. The above description of the changes which occur with a comet holds true when a comet is seen as it approaches the sun. With the aid of a diagram we will now show the usual course of a comet, and also endeavour to explain why they are sometimes seen only as they are travelhng away from the sun, and why some also suddenly appear, and. of a very large size. The earth travels round the sun, and at a nearly uniform distance, this being the usual course of a planet. A comet passes round the 206 COMMON SIGHTS sun, but not completely round it, then travels far away beyond the range of our sight, we know not where. The respective courses of a planet and comet may be understood from the following diagram : As / Np i ^(® i e The circle A B C D represents the earth's orbit round S the sun \ x y z represents a portion of a comet's orbit, which may extend to one hundred times the distance from the sun that the earth's does. If the earth were at A when the comet was at x^ the comet would scarcely be seen, as it would be so close to the sun that it would set immediately after it, and thus on account of the light would not be visible. If then the comet moved from x \^o y and z^ it would reach the point y perhaps when the earth was at B, and would thus be invisible in con- sequence of the sunlight. Then as the comet IX THE HEAYEXS. 207 moved to z, the earth would have travelled to C, and the comet would now be visible for a short time just before sunrise. It would be travelling from the sun. and at a great distance, therefore not a very noticeable object in the heavens. If, however, the earth had happened to be at the point D in its orbit when the same comet was at x, then it would have been dis- tinctly visible, and would have been in the south about midnight. AThen the earth moved on towards A, the comet would have passed round towards y, and would thus have disappeared. Viliether we see a comet distinctly and for a long period, as it approaches or moves from the Sim, depends therefore entKely upon the relative positions of the earth, the sim, and the comet. Any person, however, although not scientific, or acquainted Y^ith mathematics or astronomy, can draw a circle, can place the sun in the centre of this circle, and can make a mark to indicate the position of the earth ; then if it be 208 C03IM0X SIGHTS announced that a comet is visible in any part of the heavens at a certain hour, and is moving to^Yard, or away from the sun, he can sketch the most probable com^se of the comet^ and can then see where it is likely to move to. For example, suppose a comet were obseiTed in the month of September, and was visible at mid- night in the south-east — we can draw a circle V'C jST D E, which represents the earth's orbit, S being the sun, E the position of the earth in Sep- tember, which moves round towards D. At midnight in September the south would be in IN THE HEAYEXS. 209 the opposite direction to that of the sun ; there- fore the south-east at midnight would be in the direction EC. A very few observations would show whether the comet was moving towards or away from the sim, for if it increased in apparent size or brightness, we should know at once that it was approaching the sun. This comet if approaching the sun would move either as shown by the curved line C 31 or by the line C T P. Whichever course it fol- lowed, it would come very near to the earth, and would therefore be a much more remark- able object in the heavens than when first observed. If the comet moved in the course indicated by C T P, we should probably also see it upon its return from the sun, for the earth would have moyed round towards D, whilst the comet had travelled from C to T and round towards P. K the comet pur- sued the course shown by the line C M, we should see it clearly only when it was moving towards the sun, for as it moved awav it would be between S and M, and therefore p 210 COMMON SIGHTS behind the sun, because the earth woukl be near the point D. If in September a comet were observed at midnight in the south-west, this comet would be in the direction shown by X. Then as the earth moved on from E towards D, and the comet from X towards S, it would soon be lost to view in consequence of its approach to the sun. Sonietimes a comet will approach the sun Irom what we should call a high point in the heavens : when this is the case it may be clearly visible in the north at midnight, the sun being then in the north, but belov/, whilst the comet is above, the horizon. Some very fine comets may be seen in this position, the last brilliant comet that visited us having been during a considerable time in the north about midnight, whilst retreating from the sun. xlny novice can, however, roughly calculate whether a comet is likely to be a very remarkable object in the heavens, by drawing a circle, and placing on this a mark to indicate the earth's position, IN THE HEAVENS. 211 then sketch the position of the comet and the two courses which it may pursue. Referring to the preceding sketch, the comet vfould be said to be moving direct if its course were C M, because this is the way in which the planets move round the sun. If its course were C T P, it would be said to have a retro^ grade motion, because this is the opposite course to that w^hich the planets pursue. When it is announced, therefore, that a comet is visible in the heavens, and that it is moving towards the sun with a direct motion, a little sketch will soon enable us to judge whether the comet is likely to approach the earth, or to be visible for any length of time. We may perceive by an examination of the sketch that it would be quite possible for a comet to approach the sun, move round it, and travel away without being seen from the earth- Such a position as D, for instance, would pre- vent us from seeing the comet X, which might pass round the sun from T to 0, and thus remain invisible during its whole course. 212 COMMON SIGHTS There are various kinds of comets, or tliey may visit us in diiferent stages of development ; for tliere are — Comets without a nucleus. Comets without a tail. Comets, the nucleus of which is quite trans- parent. Comets, the nucleus of which is either opaque or solid. It is believed to be an invariable rule that the tails of comets always point aivay from the sun ; so that, whichever way a comet may be moving, it does not draw its tail after it, but the tail appears driven away from the solid or more dense portion by the action of the sun. Hence " taiV is a misnomer; for a tail never precedes any body, but ought to follow ; whereas the tail of a comet retreats from the sun before its head, and thus imitates a courtier retreat- ing from the presence of majesty. Occasionally variations from an apparent rule are observable : thus, a comet which was seen in 1823 had two tails, one of which was as IN THE HEAVENS. 213 usual turned away from the sun ; but the other, with a total disregard of all cometary etiquette, w^as turned directly towards the great luminary of our system. Many cases are recorded where a comet has possessed a tail divided into several distinct branches, some having as it were five or six tails. The size and brilliancy of the nucleus of a comet are no guides to the dimensions of the tail, some large tails being attendant upon a small nucleus, and vice versa. There are three comets in particular which be- long exclusively to our solar system, and which return at regular known intervals. These pre- sent peculiarities which are very interesting, and which have served for a fertile field of specula- tion. The first periodic comet, as these bodies are called, is named after Dr. Halley, the cele- brated astronomer. The other two are named after the tvvo astronomers who first calculated their orbits, viz., Encke and Biela. Encke's comet travels romid the sun within the orbit of 214 COMMON SIGHTS Mercury on one side, and then journeys nearly as far as Jupiter on the other. This comet has revealed two very singular facts ; first, that when near the sun, its diameter is very much smaller than when at a distance : thus the sun appears to condense the particles of which this comet is composed. Secondly, the retm^n of the comet to a certain point does not occur uniformly, but there is a gradual decrease in the period. Thus, it might occupy 1069 days and 12 hours to move completely round its orbit when we ob- served one revolution, but merely 1069 days and 8 hours dming the next ; 1069 days and 4 hours for the third, and so on with a gradually decreasing rate. These two facts have of course caused considerable speculation to be expended upon the results which might possibly happen to the various members of the system. We will now refer to the speculations and conjectures which have been offered in connec- tion with comets. Among the earlier conjectures about comets were those which we have already mentioned, IX THE HEAYENS. 215 viz., that they come as messengers of evil, or were the vehicles for conveying good spirits to other parts of the universe. A messenger with a tail about thu^ty millions of miles in length would be rather an extravagant courier to be employed by the divine Architect of nature, whose w^orks so decidedly testify that economy is one principle of the universal system. Another supposition as to the use of comets was, that they revolved a few times around our central luminary and then dropped into him, and thus •' kept the kettle boihng ;" or, in other words, supplied the losses which, it was as- sumed, the sun suffered bv oivino^ out heat and light. In an age when a blazing &e, or some sort of fire, was supposed to be the only cause of heat, such a speculation as the above did not seem absurd. ISTow, however, those who reason amongst us would not be disposed to grant either that the sun is on fire, or that it requii'es fuel to keep it going. Such a theory also might explain the finale of a comet, but it would leave its orio'in in obscuritv. 216 COMMON SIGHTS Will a comet ever run away with the earth, or run against it ? or will the tail of a comet ever surroimd the earth? are questions which have been gravely asked, and seriously an- swered. Are comets habitable ? do they pro- duce diseases or fogs ? and will they disturb the earth's motion? are considered fair subjects for inquiry. The speculations of M. Laplace upon the supposed effects whic^h might happen, assuming that a comet was solid, and that it could run foul of the earth, produced great consternation in Paris, where good situations in Paradise were sold to the credulous at a fah: market price, when a large comet became visible in the heavens. A collision is much more in character with the proceedings of a couple of intoxicated cab- men, than with those of the works of nature in which order, harmony, and arrangement are everywhere visible. In the year 1770 there was a comet which passed twice through the system of Jupiter, yet IN THE HEAVENS. 21 < it produced not the slightest effect upon the movements of Jupiter or his satellites. When a collision between a planet and a comet is spoken of, it is assumed that the comet is hurled blindly at the sun, wliilst the planet still rushes around its orbit, and that therefore it is merely a matter of luck or chance ^Yhether the two run foul of each other. Are we warranted in assuming that anything in natm-e is left to chance ? is it not more probable that the very law which brings comets towards the sun, may serve to keep them at such a distance from the planets that no disasters may happen ? A planet, like one pole of a magnet, may have a repelling as well as an attracting power ; and though at certain distances a comet might be attracted to a planet, still, if the distance decreased, this attraction might cease. It is possible, nay, almost certain, that comets have an use : it does not appear that they are required to supply the sun with fuel ; for they pass around him, and travel away into unknown regions. May they not be the agents for gather- 218 COMMON SIGHTS ing up all those gases or used vapours wliieli may be thro\^Ti off by the sun and the various planets — celestial dustmen, in fact ; who come merely when the condition is such as to require them, and which are attracted by a sort of self- adjusting law when the system requires their presence ? From our sun they may travel to another luminary, and may thus serve to maintain a balance between various portions of the uni- verse ; extracting from one group that whicli may be dispensed with, and imparting this to another where it may be required. Thus when the comet that we have spoken of as visiting the Jovian system passed twice close to the planet Jupiter, it was probably playing the part of scavenger, and relieving that system of elements which were no longer requned. It is possible also that a comet, when once called into existence, may have a definite des- tination, which may depend upon the affinity of the particles of which it is composed towards various portions of the universe. For example. IN THE HEAVENS. 219 a comet may perhaps move around two suns for a long period, until it reaches a certain state, when it might become merely the at- tendant of one of these. The comet of Encke, for example, belongs exclusively to our system ; and we see that this comet has merely a less dense or compact form than a planet, and a more elliptical orbit. This orbit is decreasing in ellipticity, whilst the comet is gradually as- suming more and more the course of a planet. Let these changes continue during many ages, and w^e shall at length have to call this comet a planet, as it will then diifer in no essential particulars from a planet with a very elliptical orbit. The fact of the comet of Encke having been observed to be gradually contracting its journey of revolution around the sun, has led to the conjecture that what we term space — that is, the intervals between the sun and the respective planets, &c. — is filled with some subtle fluid which opposes the motion of bodies, this fluid being termed a resisti7ig medium. Hence it has 220 COMMON SIGHTS been supposed tliat, in consequence of this re- sisting medium, not only all the comets, but all the planets, will eventually tumble into the sun, the moons upon their primaries, and the whole of the bodies in the universe will be bumping and knockino* a2:ainst each other. There are one or two trifling preliminaries which have to be assumed before this disastrous state of confusion could be reached, and these we will briefly consider. The belief of the existence of a resisting medium arises from the following mixture of facts and suppositions. It is a law of motion that if a material body be given an impetus in any direction, a movement will take place, and continue for ever unless some opposition be offered. So also, a comet, if flung towards the sun, would continue to move at the same rate and time, provided there were no resisting medium to oppose it. " The comet does not move uniformly ; there- fore there is a resisting medium." This rea- soning might have passed muster in a bygone IN THE HEAVENS. 221 age, when cause and effect were but little studied, when hypothesis rested upon theory, and theory upon guesses, the whole being sur- rounded by a maze of figui^es to protect the assumption from the criticism of the inquirer : but some further probabilities must now be examined before we grant any such theory as that all the comets and planets are going to tumble into the sun. In the first place, are we quite certain that comets have really been flung or launched in their orbits by some mechanical agency. If we are not certain of this, the theory of the re- sisting medium rests upon a guess ; whereas a theory ought to be based upon well-established facts. Again, let us grant the singular assump- tion that this gaseous body was launched or hurled towards the sun from some out-of-the- way locality beyond the orbit of our earth, and we are not driven to the necessity of granting that it will fall into the sun, in consequence of a resisting medium. AYe know that as the comet approaches the sun, its diameter de- 222 COMMON SIGHTS creases ; are we then certain that the sun may not, each time the comet approaches it, cause the comet to become more and more solid and less gaseous ? In fact, to become more planetary and less cometary in its constitution ? Such a change would cause the comet to decrease its period of revolution, even according to the laws of mechanics as interpreted by us ; and the body, by these transmutations, might at length take • its place in the system, as an inter-Mer- curial planet, with a density even greater than that of Mercury, and with an orbit not less elliptical. It is always an advantage to have a choice of theories ; and we are impressed with the idea that progression in Nature's vast works is so much more agreeable to reflect upon than collision, confusion, and destruction, that we trust the reader will pardon the somewhat lengthy conjectures offered upon the probable use and destination of cometary bodies. IN THE HEAVENS. 223 CHAPTEE XII. At uncertain periods and intervals there is visible near the northern portion of the hea- vens a very beautiful phenomenon, called the '• Aurora Borealis." The aurora presents during a very short time various changes, which, for the sake of distinction, have been designated by different names. The first indication of the advent of an aurora is a light appearance in the northern sky, somewhat similar to the dawn of day. This light is usually seen about one or two hours after^ sunset, and has been called the aurora twilight. This "twilight" varies in intensity, and serves as an indication of the coming aurora, which should be looked for during the evening. As the evening advances arches of light, in 224 COMMON SIGHTS form somewhat like a rainbow, may be seen to stretch from the north-east round to the north- west ; these arches are usually pale yellow or whitish. From these arches, or from some dark smoky- looking clouds which usually rest near the northern horizon, several streamers will be seen to shoot up from the north towards the heavens above us. These streamers are bright, and conamonly pale blue or pink, and they flash and rush upwards with great rapidity. A circle of either pure white or of various brilliant colom^s, with streamers shooting out from it, is frequently observed during the aurora. This circle is usually around the point in the heavens towards which the pole of a balanced magnetic needle would point, and it is called the corona. In addition to the streamers there are some- times undulations or waves of light, which flow upv/ard towards the corona or along the line of an arch. In addition to the above there are milky sort IN THE HEATEXS. 225 of clouds, which have a self-luminous appear- ance, and which prognosticate the intensity of the aui^ora. In England the aurora is not a very common phenomenon ; but in North America and in northern regions it is frequently visible. Still, if an individual is acquainted with the pre- liminary indications of the coming aurora, he may frequently observe this beautiful and mystical effect. A very beautiful aurora was visible on the evening of the 9th March, 1861 : a description of this may serve to explain the general appear- ances of the phenomenon. At a very short distance above the northern horizon, and at about half-past 8 p.m., there gradually appeared a sort of green-tinted twi- light, as though the sun were going to rise. A few dark clouds then gathered in the centre of this light, which soon varied in intensity, some faint pale-bluish streamers then shot upwards from the N.jST.E. and from the N.X.^Y. points of the horizon. These streamers reached nearly Q 226 COMMON SIGHTS overhead, but as tliey ascended tliey changed their hue, and became of a warm rosy colour. They extended east and west, lost the streamer form, and illuminated the heavens just as though some large fire were ^casting reflected light into the sky. These ajDpearances came in flashes, and there were intervals of several minutes when no streamers were visible. The aurora continued during nearly two hom^s. From observations which have been carried on during upwards of a centm^y, it is found that the greatest number of aurorse occur in the month of October, and the fewest in June. The ratio being as follows : — October, March, No- vember, September, December, February, April, Januar)^, August, May, July, June. This ratio it is believed is liable to variation, which some inquirers suppose to be periodical. It has been found that at certain periods, both during the day and night, there are cur- rents of a subtle element rushing over the earth's surface. These are usually called mag- netic or electrical currents, because they cause IN' THE HEAYEXS. 227 a magnetic needle to slightly vary, and also produce singailar effects upon the needles of the common telegraph. AYhen an am'ora oe- cm^s these disturbances are considerably in- creased, and it is sometimes almost impossible to send a telegraphic message when an aurora is in force. The aurora is seen best in the higher regions of the earth, and better in the western continent than in the eastern. From these facts we are at once led to conclude that the aurora is probably a magnetic phenomenon. We are not yet aware how the proper balance of electricity or magnetism is maintained upon and in our earth, nor are we yet made acquainted Avith the exact relation which exists between these two forces. We know that electrical storms occur at certain interrals, but we are not fully aware of the cause of these, which after all must be merely the effects of other effects. It may be then that, when there is a superabundance of magnetism in the earth, this surplus is discharged from both magnetic poles : the rapid passage of the magnetic element 228 C03IM0N SIGHTS through the atmosphere producing light. Hence it is probable, should this supposition be true, that at the same time an aurora would be visible both in the northern and southern re- gions. It is possible that this may be the case for many other reasons, which would, however, be beyond the course of this little work to adduce. A very little observation directed towards the • northern horizon soon after sunset, es- pecially in February, March, September, and October, will be rewarded by a ^^ew of the bril- liant phenomenon called the Aurora Borealis, METEOES AXD AEEOLITES. At various times of the year, but particularly in the month of August, a brilliant star-like object may be seen, which shoots along the sky for a short distance, and either disappears as though it ** went out," or bursts with a loud report. These objects are commonly called meteoes, aeeo- LiTES, or SHOOTIXG STAES. The fall of these sin- gular bodies afforded one of the many examples IX THE HEAVEXS. 229 of the danger that surrounds those men of science who believe that they have solved all the laws of nature. '' The Academy of Sciences," says 31. Arago, " declared in 17(19 that the stone picked up at the instant of its fall at Luce, by several persons who continued to perceive it until it reached the earth's surface, had not fallen from the heavens," and the savants of Europe affirmed '' that the fall of stones from the atmosphere was impossible/' As M. Arago justly remarks, " It is certain that physicists who refuse to admit any facts except those which they perceive to admit of explanation, do more injury to the progTcss of science than men who are liable to the reproach of being too credulous." It has been found that in nearly all the masses which have been ascertained to have fallen from the atmosphere, there is a prepon- derance of nickel. Some of these masses are hard, whilst otliers are spongy. We have the record of several accidents which have been caused by aerolites : and when 230 COMMON SIGHTS we consider the weight of some of these bodies, it is not remarkable that accidents should occur. In 1674, a ball weighing nine pounds killed two men on board a Dutch East Indian vessel. An aerolite fell in New Granada in 1810, and weighed upwards of sixteen hundred pounds. Globes of fire which suddenly appear and then vanish are usually termed bolides. Sometimes bolides give out a very bright light, or leave behind them a train of fire ; occa- sionally they burst into several pieces, which form those falling bodies of which we have spoken. Aerolites have afforded a fine field for con- jecture, since men of science admitted that they were possible. It has been supposed that a ring of these bodies revolves about and surroimds the sun, and that the earth passes through this ring in August, when, consequently, the greatest num- ber become visible. Other speculators imagine that they are fired out of the volcanoes in the moon. But, as we do not yet know that the lunar volcanoes are active, and we have to IN THE HEAVENS. 231 assume a Yelocity of projection of upwards of eight thousand feet per second, this conjecture is rather baseless. It may be possible that the elements of which asteroids are formed exists in space, and that these become soUdified by agencies occasionally at work, and which may be induced by the earth's electrical or magnetic state, just as water may be formed from its elements by the electric spark. THE END. LONDON : PRINTED 3T WILUAil CLO"^ES AND SONS, STAMFORD STREET. 3 1"^^/' >/. ,c\^^ "^^ x~^ ,<?-'^ ,^^ -<«-. 'I' «^. .^'""-^ ^W. x^V * ^<^ y?:^^'^ ^ ^ ^^ : ix -r. .XV r •=^;";zt^\g^ ^o- ,0- s "" '^ '' ', "^^ .^^ ^<^. -.0 o T iv; O ■^^ ^^^ ^ n - . ^ -^-^?r^ :%.